Updated xUnit and Autofixture to latest versions on a solution basis
Moved ScriptCsAutoDataAttribute and linked it into all test projects
Extracted interface IScriptHost from ScriptHost to allow automocking.
Refactored all tests in ScriptCs.Engine.Roslyn.Tests
Minor change
Merge pull request #385 from khellang/test-refactor

Refactored tests for Roslyn engine to new setup