docs(ember): Add note for tying karma start to App.initialize

Tests against an ember application should not start until the
App has completed initializing.  The note and suggested
bootstrap method demonstrate how to deactivate karma autostart
and how to explicitly start karma at the appropirate time.

Closes #1012
Merge branch 'master' of https://github.com/jefflage/karma

Conflicts:
	docs/plus/08-emberjs.md