adding a bunch of simple tests for the guard.
Adding test-results to .gitignore
Change type signature of NotNullOrEmpty to string since it's only used for strings.
Fix test for NotNullOrEmpty passing check.
Add simple guard tests for SetParser() method from Converter.
Change exception type for null argument to ArgumentNullException.
Add new test for NotNull with provided message.
Support providing exception messages for Guard.NotNull()
Fix argument name passing tests. They were not checking for argument name existance in ex.Message.
Converter.SetParser now uses Guard.NotNull for brevity.
Remove Converter.SetParser and Converter.SetTemplater

Both methods are not used and thus not needed. OMG, I should've checked
before I got into writing unit tests for that. My bad.