Two small changes: string formatting error and edit to success message

Traceback (most recent call last):
  File "/Users/jessamyn/.virtualenvs/piprot/bin/piprot", line 8, in <module>
    load_entry_point('piprot==0.1.2', 'console_scripts', 'piprot')()
  File "build/bdist.macosx-10.8-intel/egg/piprot/piprot.py", line 218, in piprot
  File "build/bdist.macosx-10.8-intel/egg/piprot/piprot.py", line 197, in main
TypeError: not all arguments converted during string formatting

So I converted all the multiline strings to use the preferred PEP 8 style of line continuation inside parentheses. I also made the success message something we can (hopefully) all relate to.