Use TestMustDing helper method
Replace Fakes with simple mock object

Fakes are handy, but require Visual Studio Professional.
To enable folks using Express, I added a mock interface
for the bits that need mocking.
Merge branch 'master' of https://github.com/lzybkr/PSReadLine

Conflicts:
	PSReadLine/PublicAPI.cs
More cleanup from removing Fakes