Clean up double tap code to make it more legible. Also switch from
window animations to a custom ViewPropertyAnimator to work around a
Samsung device bug. Also clean up a little animation glitch in the
source chooser fragment.

Also bump version code in prep for 2.0.1.
Merge branch 'master' of https://github.com/romannurik/muzei
Switch from OPEN_DOCUMENT to GET_CONTENT for gallery picker. Also fix bug #66, which was caused by a math error
Fix issues #111 and #98
Add external contributions to about body