Add "id", "icon" and "class" options support for tab pane.
Do not render pane if it has no content (arguable: need option for that)
Remove hardcoded "icon-" prefix
Merge remote-tracking branch 'isc/master'

Conflicts:
	test/test_tabs_helper.rb
Add "in" class to active tab with fade effect.
Tabs helper test refactoring
Wrong accordion.html fixture
Merge pull request #2 from Darkside73/master

Extending options for the tab pane