Improved test coverage on MockDirectory and MockDirectoryInfo
Implemented MockDirectory.GetRootDirectory
Reimplemented MockDirectory.Move (previous system failed a new test I wrote)
Implemented MockFile.CreateText
Implemented MockFileInfo.MoveTo

Signed-off-by: Martin Evans <martindevans@gmail.com>
Merge pull request #29 from martindevans/master

Improved test coverage for MockDirectory (and some more methods implemented)