drop htmlhint given htmllint gives us most of the coverage we need here

CHANGELOG.md

-Bootstrap uses [GitHub's Releases feature](https://github.com/blog/1547-release-your-software) for its changelogs.
-
-See [the Releases section of our GitHub project](https://github.com/twbs/bootstrap/releases) for changelogs for each release version of Bootstrap.
-
-Release announcement posts on [the official Bootstrap blog](https://blog.getbootstrap.com) contain summaries of the most noteworthy changes made in each release.

build/.htmlhintrc

-{
-  "alt-require": true,
-  "attr-lowercase": true,
-  "attr-no-duplication": true,
-  "attr-unsafe-chars": true,
-  "attr-value-double-quotes": true,
-  "doctype-first": true,
-  "doctype-html5": true,
-  "id-class-value": true,
-  "id-unique": true,
-  "space-tab-mixed-disabled": true,
-  "spec-char-escape": true,
-  "src-not-empty": true,
-  "tag-pair": true,
-  "tagname-lowercase": true,
-  "title-require": true
-}

package.json

@@ -42,7 +42,7 @@
     "js-launch-cloud": "ruby -r webrick -e \"s = WEBrick::HTTPServer.new(:Port => 3000, :DocumentRoot => Dir.pwd, :Logger => WEBrick::Log.new('/dev/null'), :AccessLog => []); trap('INT') { s.shutdown }; s.start\" & grunt saucelabs-qunit",
     "js-test-cloud": "npm-run-all js-test-dep js-launch-cloud",
     "docs": "npm-run-all docs-compile docs-lint",
-    "docs-lint": "htmlhint --config build/.htmlhintrc _gh_pages/ js/tests/visual/ && htmllint --rc build/.htmllintrc _gh_pages/*.html _gh_pages/**/*.html js/tests/visual/*.html",
+    "docs-lint": "htmllint --rc build/.htmllintrc _gh_pages/*.html _gh_pages/**/*.html js/tests/visual/*.html",
     "docs-compile": "bundle exec jekyll build",
     "docs-serve": "bundle exec jekyll serve",
     "docs-github": "shx echo 'github: true' > $npm_config_tmp/twbsconfig.yml && npm run docs-compile -- --config _config.yml,$npm_config_tmp/twbsconfig.yml && shx rm $npm_config_tmp/twbsconfig.yml",
@@ -80,7 +80,6 @@
     "babel-preset-es2015": "^7.0.0-alpha.7",
     "clean-css-cli": "^4.0.12",
     "eslint": "^3.19.0",
-    "htmlhint": "^0.9.13",
     "htmllint-cli": "^0.0.6",
     "node-sass": "^4.5.2",
     "nodemon": "^1.11.0",