According to the docs, you just need to apply the `navbar-nav` to an
`<ul>` tag in a list-based navbar. In fact, `navbar-nav` seems to
override all the css properties set by `nav`.
Also, `nav-item` class should be used only for `<li>` tags, or in
conjunction with `<a>` tags to entirely avoid the list-based approach.
This commit removes the redundant `nav` class from `navbar-nav` `<ul>`
tags, moves `nav-item` from `<a>` tags to `<li>` tags and properly
adds `nav-item` class to `<li>` tags where missing.
Refs:
* https://v4-alpha.getbootstrap.com/components/navs/
* https://v4-alpha.getbootstrap.com/components/navbar/#nav
* Remove IE compatibility mode meta tag from docs, examples, and JS tests as we no longer support IE9 and IE8
* update and remove some IE bits from our supported browser page
* update introduction.md to match
* reword starter template intro
faster and easier to test/develop js functionality not represented in unit tests, and gives us
a playground for interactions, etc.
It also makes it so developing javascript is now decoupled form jekyll, which should make everything
faster and less painful.
This commit also reverts my filter commit 9900771aa7
which broke scrollspy for dropdowns.
