[Array Extensions] Remove sample test
[Array Extensions] Add firstObject and lastObject methods
[Array Extensions] Add tests for arrays
[Error Extensions] Add convenience method for creating Errors with domain, code and description
[Array Extensions] Add map and select methods and their appropriate tests
Merge branch 'array_extensions'
Merge branch 'error_extensions'

Conflicts:
	PMExtensions.xcodeproj/project.pbxproj