Add internal documentation building via YUIDoc

Run `npm run docs`

Taken directly from Ember.js with minor changes, with exception that
generator will also create HTML docs as well as JSON data. We can fall
back on this until the ember-cli.com site includes this API
documentation.
Add doc signatures for EmberApp

Extremely minimal doc comment blocks. Not yet qualified to complete.
Add documentation about documentation
Implement {{content-for 'head'}}.
Merge pull request #2153 from rwjblue/implement-content-for

Implement {{content-for 'head'}}.
Update broccoli-asset-rev.
Merge pull request #2167 from abuiles/update-broccoli-assets-rev

Update broccoli-asset-rev.
Update CHANGELOG.md.

Prepare for 0.0.47.
Use symlinking.
Bump version.
Merge pull request #2125 from stefanpenner/symlinking

WARP SPEED
Fix livereload (with and without CSP).
Merge pull request #2176 from rwjblue/fix-live-reload-with-csp

Fix livereload (with and without CSP).
Update ember-cli-inject-live-reload.

Now properly injects the script tag in a CSP safe way.
Merge pull request #2179 from rwjblue/updates-inject-live-reload-again

Update ember-cli-inject-live-reload.
Update broccoli dependencies to improve performance.

When the current version of broccoli-filter is used with a directory that contains symlinks
(like something from static-compiler or merge-trees), and kitchen-sink-helpers less than 0.2.5
is used, none of the symlinks can use cache (since we are comparing hashes of the symlinks
which are recreated for each built).
Merge pull request #2182 from rwjblue/update-broccoli-deps

Update broccoli dependencies to improve performance.
Fixes 2094 by enabling addon/index.js
Merge pull request #2146 from ef4/fix-2094

Allow `addon/index.js`
Update CSP addon.

Now uses `Content-Security-Policy-Report-Only` by default.