Update .travis.yml

[techdragon]

Test against python 3.4, all the cool kids are doing it. ;-)

[theju]

Started the process of migrating to Py3 but there are a few roadblocks:

• Suds used by EPay is not supported on Py3
• WePay python sdk is not supported on Py3
• FormEncode used for travis is not supported on Py3
• Some instances of Py2 code in the merchant code base (these are being removed as and when we come across).

I don't think we are inclined to go the route of forking these packages and maintaining them.

[tuxcanfly]

FormEncode is only a util for the build process, but suds and wepay sound like major bottlenecks.

[theju]

@tuxcanfly That's right but would be great to have your opinion on continuing with Travis.

[tuxcanfly]

There are too many external variables affecting the tests, lets put open issues and features on top priority and get back to travis later.