Code review comment for lp:~ev/oops-repository/whoopsie-daisy

I've added a commit to handle unicode data in OOPSes by setting a default_validation_class of utf8. The previous behavior was causing exceptions as submissions were made to Ubuntu's crash database:
https://pastebin.canonical.com/62948/

I originally implemented this by encoding unicode dictionary keys and values as utf8 in oops-repository, but then I noticed the comment in DESIGN.txt about the columns all being strings. If that interpretation is incorrect, do feel free to take r27 instead of r28.