Added support for badges in TabBar icons

Added support for TabBar icon badges using the attribute badge in the
tab directive.

Ex: <tab icon-on="icon ion-ios7-person" icon-off="icon
ion-ios7-person-outline" href="#/tab/myprofile" badge="3">

I’ve used the colors of the TabBar itself but inverted for the badge. I
don’t know if you’ll want to merge this straight on but I think it can
help as a start point for this feature. I’ve tried to do it as
integrated as possible.
Allow dynamic badges

Allows the badge parameter to accept a variable binding so it updates
automatically.
Tab badge css fixes

Fixes some problems with some types of tab bars.
Added tests for TabBar badges

Adds tests for the HTML version and the Angular directive.
More support for Tab Badges

Added support for Tab Badges into tabBarController and tabBarView.
Cleanup in angular directive

Removed a log and an unused old variable.
Added unit tests for TabBar badges and tabControllerItem

Added unit tests and adapted old ones to test correctly the Tab Bar
badges.
Added unit tests for tabControllerItem (also with badge tests).
chore(travis): make "do-not-build-on-pull-request" work