security/py-ecdsa: Correctly enable Python 3.x support

ecdsa module already (0.11) supports Python 3.x [1] and has just been
tested on Python 3.4 [2].

Correctly enable Python 3.x support accordingly.

White I'm here, whitespace align.

[1] https://github.com/warner/python-ecdsa/blob/python-ecdsa-0.11/setup.py#L104
[2] https://github.com/warner/python-ecdsa/pull/26

QA under Python 3.4:

Ran 43 tests in 10.659s - OK
5922 tests of inverse_mod completed. 0 errors detected.

Approved by: portmgr (blanket)