Removed obsolete class MockSolutionFileContents
Created class FilePath to encapsulate comparing file paths (better than dealing with them as strings)
ExistingMixinFileTest is no longer needed
Add ability to clear out code from an existing code behind
Split up logic for GetValidPMixinFiles to make it easier to debug
Updated AssemblyResolver to use TaskFactory
FireOnSolutionOpen in Test
Disable EagerlyResolveReferences - race condition
Reverted ProjectFile in IntegrationTestBase to use pMixins.CodeGenerator.Tests (so tests could reference existing classes) but override FileWrapper to return empty file contents for AssemblyInfo (to prevent reading DisableCodeGeneration attribute)