move off of Test::MockObject

This patch replaces the use of Test::MockObject with a real Dist::Zilla object.

Test::MockObject is a bit of a dubious proposition for testing, as it can hide errors and confuse code that uses it... (http://hashbang.ca/2012/07/26/mocking-lwpuseragent-properly) ... it also has some downstream dependencies that don't currently install under the upcoming version of Test::Builder (0.98_05).