fix(photo): remove accidentally copypasted line from vkPVSaveAndMover()
refactor(ajax/performRequest): accept custom callback

Refactor performRequest so that it accepts callback instead of
sending message event on window object.

This closes #88.
refactor(ajax): accept custom performRequest as second argument

This closes #90.
fix(app): rename test/unit/init to test/unit/app

This closes #89.