Add Tabs module to XBlock
Add tests for TabsEditorDescriptor
Add templates according to new tabs logic
adds docs, fixes super(..) call, removes id from context, adds empty tabs by default
adds doc, fixes typo, renames files and creates tabs folder for tabs templates
adds tabs support for HTMLModule
moves save function to templates, provide more common mechanism to define save functions
cleans old names
adds support for tab css
adds testing information
adds support for single tab: do not show tabline
adds test video files to gitignore
adds docstring about having only one inner editor
adds docs, fixes callbacks conditions, adds code clean up
fixes latex saving to codemirror w/o updating tinymce
renames display to edit
simplifies python code in template
adds i18n to  tabnames
Spliting tab styles from codemirror styles.
adds i18n support to tab names