Python 3. Update Travis CI config, change web.py example into bottle

This is related to #38.

This may help fix Travis CI build for Python 3.3.

Since web.py does not support Python 3.x I replaced example and test into bottle.

I'm hoping that bottle example could be a good replacement since it's pretty simple and well-known.


Unfortunately Travis CI still fails for Python 3.3 job during "python setup.py install" call.

Detailed log is here:

https://travis-ci.org/diyan/gevent/jobs/14596485


I also tried merge code from master into python3 branch on my local workstation but it did not help.

Would like to give big thanks to author and all contributors and looking forward for more activity on Python 3 support.