Implemented requested changes.

>Happy to pull in your commits... just before I do that, would you mind doing a cleanup for me?

>* unused stuff (TERMSAVER_DEFAULT_CACHE_FILENAME seems not used)
     * so no changes to .gitignore, constants.py, I presume
* trailing blank spaces
* classes and variables notation (underscores instead of pascal case)
     * I realize it is not the best, but I'd rather stick with one standard

>In addition, one bug fix:

>* Because of the threading, the exit command (Ctrl+C) does not work anymore. You can easily fix that by appending to line 150: threads[-1].daemon = True