Added support for operating systems where default Python version is 3

Hello. I tried compiling DynamO on Arch Linux – I succeeded, but since Arch uses Python 3 by default (i.e. the `python` command evokes `python3`) I had to change shebangs in a few files from `#!/usr/bin/env python` (which runs `python3` in Arch) to `#!/usr/bin/env python2`, which should run `python2` on any system.

It doesn't work with Python 3, because of use of the deprecated `print "something"` statement, which became `print("something")` in Python 3.

By the way, DynamO is really great, thanks for it! :+1: