Remove buggy theme file url function

The idea was that people could supply their own versions of certain
style and script files by just dropping them into their child theme
directory. However, the function for determining the correct URL for
these assets was failing in some environments. People can still supply
their own versions if they unenqueue the original and then re-enqueue
with a new URL.
Update changelog for 1.2.2
Bump version to 1.2.2
Merge branch 'release-1.2.2' into develop
Version 1.2.2