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
try clearing npm cache on appveyor build
this shouldn't work
more bad ideas
node on windows should be outlawed
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).