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
Use injection as example in initializer blueprint

Fixes #2147
Merge pull request #2148 from jgwhite/fix-2147

Use injection as example in initializer blueprint
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.