Images are now stored in tempfiles, so they only have to be downloaded once.
Improved performance (cpu time went down from 25%+ to 1-2%), and made it so that tweets are not cut off if the screen is too narrow.
Merge branch 'imagefiles'

Conflicts:
	main.py
	tweetviewer.py

merging my imagefiles branch (a branch that used tempfiles for images) into my master branch.
Removed debugging statements