python3 compatibility fix
From [P3 what's new page](http://docs.python.org/3.0/whatsnew/3.0.html)
string.letters and its friends (string.lowercase and string.uppercase) are gone. Use string.ascii_letters etc. instead. (The reason for the removal is that string.letters and friends had locale-specific behavior, which is a bad idea for such attractively-named global “constants”.)
| author |
Catalin Costache <catacgc@gmail.com> |
| date |
Mon, 23 Dec 2013 01:02:52 +0200 |
| parents |
de2735512614 |
| children |
a9e32bdb260b |
08d62006bc7d70b00980a76dec98035c0be1d9b4 v0.1.0
46cb98ff7fe08c1a70af90d4a92d427d50000d4d v0.2.0
0f88e9f35bf1f2acab75065f46766976ecdb7d7b v0.3.0
aef3e059452cf2ed2299b044906bc2823c90f552 v0.3.1