R1:0d5b0f21ad2b

Convert author/message encoding if not UTF-8

Test Plan:
used the reparse.php script for reparsing commit messages and saw the
correct author name (and mapped correctly as a phabricator user) in diffusion.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, epriestley

Differential Revision: 1059