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
ensure line + col information is also displayed
Merge pull request #2246 from stefanpenner/more-errors

ensure line + col information is also displayed
Remove duplicate writeError.

Both the livereload server and the watcher were listening to the `watcher`'s `error`
event which caused the same error to be printed twice.

The `didError` in `livereload-server` is superfluous (it cannot run
without `wacther` running and `watcher` already has a `didError` that
does the right thing).

Moved the tests from livereload-server-tests to watcher-tests.
Merge pull request #2253 from rwjblue/remove-duplicate-error

Remove duplicate writeError.
Merge pull request #2106 from hparra/feature-add-yuidoc-building

Add yuidoc building
Tweak helper blueprint

Fixes #2228
Merge pull request #2257 from jgwhite/tweak-controller-blueprint

Tweak helper blueprint
Streamline initializer and service blueprints

Fixes #2259
Merge pull request #2260 from jgwhite/streamline-exports

Streamline initializer and service blueprints
Add ember-export-application-global to default app blueprint.
Merge pull request #2270 from rwjblue/export-global

Add ember-export-application-global to default app blueprint.
correct typo
Merge pull request #2274 from dondanhill/master

correct typo