Hook up FactCheck to Travis

Hi,

I've added some functionality to make it easy to use FactCheck in custom packages with Travis. I also hooked up FactCheck.jl with Travis to show how this works.

* added getstats() which return the total numbers of successes, errors, failures and nonsucccessful (== errors+failures)
* adding `exit(getstats()["nNonSuccessful"])` to the end of the tests returns with non-zero in case of error

Could you please set up travis for `zachallaun/FactCheck.jl`, then replace line 14 with 13 and put your email in .travis.yml (I had to make it use my fork to be able to test it)?

Thanks!

Rene