Uncomment line for Travis

I commented the part that run the tests hoping that it would pass, but
instead returned me this error:

>Please override the script: key in your .travis.yml to run tests.
>The command "false" exited with 1.
>Done. Your build exited with 1.

By checking the website, I found that:

>In case script key is not provided in .travis.yml for Python projects,
> Python builder will print a message and fail the build.

I uncommented one line to test if it will pass.

Related to #24.