Use WPTextView and switch to Open Sans in other widgets used in stats.
Use WPTextView (and Open Sans) in the bar chart Tooltip item.
Use Open Sans in the bar graph.
Merge branch 'develop' of https://github.com/wordpress-mobile/WordPress-Android into 1669-Stats-open-sans

Conflicts:
	WordPress/src/main/res/layout-sw600dp/stats_visitors_and_views_fragment.xml
Missed one file when switched to all TextViews to WPTextView
Another TextView that I missed in the previous commits
Use TypefaceCache rather than loading new typeface. props @nbradbury
Use view.getContext rather of getActivity that could be null.
Merge pull request #1768 from wordpress-mobile/issue/1669-Stats-open-sans

Use Open Sans in Stats