[Observium] poller-wrapper and python3

Hi,

some modern system (like ubuntu 15.04) used python3 by default.

Since old poller-wrapper not compatible with python3, today I added experimental *poller-wrapper3.py* which should work with both (2.x, 3.x) python versions.

Check wich default python version used in your system: /usr/bin/env python -V Python 3.2.3

If default is 3.x, than use new wrapper in your crontab.

Note, in python3 required additional PyMySQL module (since MySQLdb unavialable for python3). In ubuntu/debian install by this cmds:

sudo apt-get install python3-setuptools sudo easy_install3 pip sudo pip3 install PyMySQL

How to install on other systems I do not know, welcome your tips.