migrate tests from mox to mock

[lelutin]

mox has been left for dead by google in 2012. also the release that's available on pypi is buggy. the bug that scout's tests are encountering is fixed in the debian package with a patch on top of the released code.

This is a pretty bad state of affairs.. tests should be migrated away from mox to use the now standard mock library:

https://pypi.python.org/pypi/mock