Will/fix travis build

Frighteningly enough, the Travis builds were not reporting failure even though tests were failing!  Tests were passing until my last commit, though.

Adding the "-e" option to the script ensures that the exit code of a failing command is passed to the script caller, in this case Travis.  I've verified that this changes the status code from 0 to 1 when calling `./run_tests.sh` without the import fix.

@jzoldak