parallelize the tests using Travis CI's build matrix
fix an error in retrieving sql result
fix the bug that chars are not converted to lower

it will result in carboncopy does not be disabled when a user is removed
and if a new user register with the same user name and bind with the
same resource, the carboncopy will be enabled for this resource.

That's why the ejabberdctl_SUITE fails
when it goes after the carboncopy_SUITE