Less strict version check in setup.py

The check `sys.version_info >= (2, 7, 7)` evaluates to True on Python 2.7.7, causing an exception to be raised when trying to install. This change increases the limit to `(3, 0, 0)`, so installation is allowed on all future 2.7.x Python versions, but not Python 3+.

Alternatively, if you want to be more strict, you could use `(2, 7, 8)`, but I don't think any future 2.7.x versions will cause any issues.