Adds ProductViewModelSpec #2.

Fixes bug found after running the spec.
Removes XCodeBuild action 'build-tests'. #2

This action is not supported in xcode-build cmd line tool, it
was supported in xctool.
XCode rake tasks now use #run instead of #send. #2

The run method verifies if the given action is valid.
Replaces Kiwi for Specta. #2

Specta specs are cleaner than Kiwi due to use Expecta matchers.

Cocoapods 0.34.rc2 was needed because Specta did not compiled with
XCode 6.0.1: http://stackoverflow.com/questions/24275470/xctest-xctest-h-not-found-on-old-projects-built-in-xcode-6
[WIP] Migrates ProductViewModelSpec from Kiwi to Specta. #2