Updated any images larger than 24x24 to that size since that is what is displayed on the site anyway. Any images not in png were converted to match as well.
Merge branch 'master' of https://github.com/jdavis/twofactorauth into resized_icons
Add US Bank, closes #131
Update README with icon guidelines as per #103
Merge pull request #103 from RichJeanes/resized_icons

Updated site icons
etrade.jpg -> etrade.png
Fixing merge conflict