Code cleanups, mechanize -> requests, VXCage support, command line changes etc.

- Changed whitespace from tabs to 4 spaces.
- Changed from mechanize to requests library (just feels better)
- Only saves file to disk if asked to do so (with the now optional parameter -o / --outfolder)
- Added the ability to upload downloaded samples to a VXCage malware repository
- Changed logging from print statements to python logging module (prettier)
- Ability to provide API key as a command line switch (hate hardcoded API keys as anyone who can run the code has the key as well)
- Made pull_daily_list() from a iterable to a generator using yield (saves memory)