Update grid docs for form layouts

- Add container to fix padding in mobile views
- Add large and small variations
- Cross link grid classes and mixins
- Fix up some words

docs/components/forms.md

@@ -332,65 +332,89 @@ Because of this, you may need to manually address the width and alignment of ind
 
 ### Using the Grid
 
-For more structured form layouts, you can utilize Bootstrap's predefined grid classes (or mixins) to create horizontal forms. Add the `.row` class to form groups and use the `.col-*-*` classes to specify the width of your labels and controls.
+For more structured form layouts that are also responsive, you can utilize Bootstrap's [predefined grid classes](/layout/grid/#predefined-classes) or [mixins](/layout/grid/#sass-mixins) to create horizontal forms. Add the `.row` class to form groups and use the `.col-*-*` classes to specify the width of your labels and controls.
 
 Be sure to add `.form-control-label` to your `<label>`s as well so they're vertically centered with their associated labels.
 
 {% example html %}
-<form>
-  <div class="form-group row">
-    <label for="inputEmail3" class="col-sm-2 form-control-label">Email</label>
-    <div class="col-sm-10">
-      <input type="email" class="form-control" id="inputEmail3" placeholder="Email">
+<div class="container">
+  <form>
+    <div class="form-group row">
+      <label for="inputEmail3" class="col-sm-2 form-control-label">Email</label>
+      <div class="col-sm-10">
+        <input type="email" class="form-control" id="inputEmail3" placeholder="Email">
+      </div>
     </div>
-  </div>
-  <div class="form-group row">
-    <label for="inputPassword3" class="col-sm-2 form-control-label">Password</label>
-    <div class="col-sm-10">
-      <input type="password" class="form-control" id="inputPassword3" placeholder="Password">
+    <div class="form-group row">
+      <label for="inputPassword3" class="col-sm-2 form-control-label">Password</label>
+      <div class="col-sm-10">
+        <input type="password" class="form-control" id="inputPassword3" placeholder="Password">
+      </div>
     </div>
-  </div>
-  <div class="form-group row">
-    <label class="col-sm-2">Radios</label>
-    <div class="col-sm-10">
-      <div class="radio">
-        <label>
-          <input type="radio" name="gridRadios" id="gridRadios1" value="option1" checked>
-          Option one is this and that&mdash;be sure to include why it's great
-        </label>
+    <div class="form-group row">
+      <label class="col-sm-2">Radios</label>
+      <div class="col-sm-10">
+        <div class="radio">
+          <label>
+            <input type="radio" name="gridRadios" id="gridRadios1" value="option1" checked>
+            Option one is this and that&mdash;be sure to include why it's great
+          </label>
+        </div>
+        <div class="radio">
+          <label>
+            <input type="radio" name="gridRadios" id="gridRadios2" value="option2">
+            Option two can be something else and selecting it will deselect option one
+          </label>
+        </div>
+        <div class="radio disabled">
+          <label>
+            <input type="radio" name="gridRadios" id="gridRadios3" value="option3" disabled>
+            Option three is disabled
+          </label>
+        </div>
       </div>
-      <div class="radio">
-        <label>
-          <input type="radio" name="gridRadios" id="gridRadios2" value="option2">
-          Option two can be something else and selecting it will deselect option one
-        </label>
+    </div>
+    <div class="form-group row">
+      <label class="col-sm-2">Checkbox</label>
+      <div class="col-sm-10">
+        <div class="checkbox">
+          <label>
+            <input type="checkbox"> Check me out
+          </label>
+        </div>
       </div>
-      <div class="radio disabled">
-        <label>
-          <input type="radio" name="gridRadios" id="gridRadios3" value="option3" disabled>
-          Option three is disabled
-        </label>
+    </div>
+    <div class="form-group row">
+      <div class="col-sm-offset-2 col-sm-10">
+        <button type="submit" class="btn btn-secondary">Sign in</button>
       </div>
     </div>
-  </div>
-  <div class="form-group row">
-    <label class="col-sm-2">Checkbox</label>
-    <div class="col-sm-10">
-      <div class="checkbox">
-        <label>
-          <input type="checkbox"> Check me out
-        </label>
+  </form>
+</div>
+{% endexample %}
+
+Grid-based form layouts also support large and small inputs.
+
+{% example html %}
+<div class="container">
+  <form>
+    <div class="form-group row">
+      <label for="lgFormGroupInput" class="col-sm-2 form-control-label form-control-label-lg">Email</label>
+      <div class="col-sm-10">
+        <input type="email" class="form-control form-control-lg" id="lgFormGroupInput" placeholder="you@example.com">
       </div>
     </div>
-  </div>
-  <div class="form-group row">
-    <div class="col-sm-offset-2 col-sm-10">
-      <button type="submit" class="btn btn-secondary">Sign in</button>
+    <div class="form-group row">
+      <label for="smFormGroupInput" class="col-sm-2 form-control-label form-control-label-sm">Email</label>
+      <div class="col-sm-10">
+        <input type="email" class="form-control form-control-sm" id="smFormGroupInput" placeholder="you@example.com">
+      </div>
     </div>
-  </div>
-</form>
+  </form>
+</div>
 {% endexample %}
 
+
 ## Checkboxes and radios
 
 Checkboxes are for selecting one or several options in a list, while radios are for selecting one option from many.