Documented IDirectoryInfo by taking documentation comments from
System.IO.DirectoryInfo
Documented IFileInfo by taking comments from System.IO.FileInfo
Documented IFileSystemInfo by taking comments from System.IO.FileSystemInfo
IDirectoryInfo should inherit IFileSystemInfo since System.IO.DirectoryInfo inherits
from System.IO.FileSystemInfo

Could avoid using an abstract FileSystemInfo class here but not sure it's worth
the effort for this particular case and it wouldn't really give us anything since these
core classes shouldn't change much if at all once completed.
Removed unneccessary conversion
Documenting some constructors
Merge branch 'master' of https://github.com/Haacked/Rothko into develop
Merge pull request #5 from pmacn/develop

Added documentation and made IDirectoryInfo inherit IFileSystemInfo