Do not build target Alcatraz-Test when running (only when testing)

Uncheck AlcatrazTests to be builded when running. This allow anyone to build the most recent version of Alcatraz without having to install CocoaPods.
See https://github.com/mneorr/Alcatraz/pull/84#issuecomment-29205131.

![alcatraz-schemes-test](https://f.cloud.github.com/assets/1041337/1616015/a975390a-5603-11e3-9d94-74eb3da75e75.png)