Cleaned up billing tests a bit.

Removed imports in the middle of test cases

Removed statement to delete all billing reports.  There aren't any in
the DB for the tests, so it was just a no-op.
Handle non-ascii usernames when generating reports
Merge pull request #809 from pculture/billingfixes

Billingfixes
Add language number back to the billing records

Moved code to generate the data for the CSV file to its own class.
It's starting to get a little complicated now.

Started new test class that uses factory functions instead of
fixtures.
Merge pull request #810 from pculture/billingcounts

Add language number back to the billing records