Remove the test_diffing unittest
Remove the test_diffing unittest

This was failing after the changes to the diffing page.  I'm thinking
that it's not really that useful since the template code is quite
straightforward.  Most of the complexity is in the calc_changes()
function of babelsubs, which does have tests.

eloquence/unisubs,eloquence/unisubs,eloquence/unisubs,pculture/unisubs,pculture/unisubs,norayr/unisubs,ofer43211/unisubs,wevoice/wesub,ofer43211/unisubs,ReachingOut/unisubs,wevoice/wesub,norayr/unisubs,ReachingOut/unisubs,wevoice/wesub,pculture/unisubs,ofer43211/unisubs,norayr/unisubs,ReachingOut/unisubs,eloquence/unisubs,ofer43211/unisubs,norayr/unisubs,ReachingOut/unisubs,pculture/unisubs,wevoice/wesub