updated to NuGet 2.7
added missing guard clauses
Merge pull request #454 from adamralph/guard-clauses

Updated to NuGet 2.7 and added missing guard clauses
Fixing small bug in ShouldNotReturnNonManagedAssemblies Test
See here: https://github.com/scriptcs/scriptcs/commit/a07ea4d2006be5338d51add0fdc83caa56d3a193#L5R67
Merge pull request #457 from johnduhart/testfix

Fixing small bug in ShouldNotReturnNonManagedAssemblies Test