Fix runtime warning Applications are expected to have a root view controller at the end of application launch.

Reference:
http://stackoverflow.com/questions/7520971/applications-are-expected-to-have-a-root-view-controller-at-the-end-of-applicati
Convert to ARC.
Update .gitignore
Stop tracking .xcuserstate and .xcsettings, consistent with updated .gitignore.
Use Xcode menu item Refactor to update to modern objective C syntax.
Stop tracking .xcuserstate.
Merge branch 'dev'