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
Little changes

More to follow, tomorrow.
Huge Changes to README and rht.py!!

Please try out the command line functions in rht and let me know what
you think!
Lots of edits: Look at the README!
Merge pull request #3 from Schudel888/master

Command line functions added.