show proper error message when viewing Customizer in IE8

update explanatory comment about iOS date/time inputs bug

add button to toggle the optional theme when viewing the docs

Conflicts:
	dist/css/bootstrap.css.map
	dist/css/bootstrap.min.css
	docs/assets/css/docs.min.css
	docs/dist/css/bootstrap.css.map
	docs/dist/css/bootstrap.min.css

The validator doesn't choke anymore on this and even though it's not spec compliant, it's needed for some IE versions. So until we move favicon.ico in root, this should do the job.

Closes #13090.
[skip sauce]

Per:
* http://jsbin.com/purer/2/edit
* https://github.com/cvrebert/bs-css-hacks/blob/6e8aa78384a005b007fc45327c9516dcf6ec0f30/README.md#ios-temporal-input-line-height
Thanks @mdo <3

[skip sauce] [skip validator]

Conflicts:
	docs/assets/css/docs.min.css

Reassigned minification of CSS files to the cssmin task.

add missing event namespacing in modal.js

Reassigned minification of CSS files from the less task to the cssmin
task

add [skip sauce] and [skip validator]

removes the extra newline added in the previous commit

add extra newline to .travis.yml that I'll remove momentarily

change note in .resizable() mixin for accuracy

Sync tooltip & popover docs