TIFF and ICNS addition to NSString+FastImageSize

OK, I did the Fork and Pull request thing... I probably did not do this the way it is supposed to be done since I reformatted the file to my style (changing where {}'s are, indenting, spacing, etc.) so it is a lot less obvious exactly what the changes are but basically I added the two methods and added calls to them similar to the JPEG call and just after it.