Bok choy tests output XUnit reports

Output test results from the bok-choy test suite to "reports/bok_choy_xunit.xml"

The results include the full package name (`acceptance.tests.test_ora.OpenResponseTest`).  I couldn't get nose to exclude the top-level packages, but I think this is actually what we want, since it will cause Jenkins to group the tests together.

@jzoldak