Command line functions added.

>>>python rht.py -h #Displays the README

>>>python rht.py -p #Displays default params (Not implemented yet!)

>>>python rht.py file.fits #Runs rht('file.fits') if it's a readable
image

>>>python rht.py directory_name #Runs rht() for each readable image
therein, using main('directory_name')

>>>python rht.py #Interactively asks for filename input