Add GoToImplementation completer command for CSharp completer
Add GoToImplementationElseDeclaration completer command for CSharp completer
Make GoTo consider (and prefer) implementations for CSharp completer
Add tests for CsCompleter's GoToImplemention and GoToImplementionElseDeclaration
Merge pull request #2 from mispencer/OmnisharpGotoImplemention

Add GoToImplemention to C# completer