Add Travis CI configuration

This add simple configuration for Travis CI. 

This is for fixing #69

For testing I have enabled travis ci for my branch.

Result is here: https://travis-ci.org/chevah/twistedchecker/builds/23504621

One tests is still failing... it is also failing on my local computer.... I will try to fix the test in a separate ticket.

Please let me know if you find this useful.

Thanks!