Travis's added

Hi,

I've provided travis script.
It has been built for Plone 4.3 and for Plone 4.2 here [Travis build #3](https://travis-ci.org/bogdangi/collective.formcriteria/builds/5223766)
But I'm not sure about PILwoTk and I drop it from buildout.
Can I merge it?

Best regards,
Bogdan.