BLD/FIX: use `set -e` to to exit on failure of any command in travis build. (#118)
BLD/FIX: use `set -e` to to exit on failure of any command in travis build. (#118)

See http://steven.casagrande.io/articles/travis-ci-and-if-statements/ and https://github.com/travis-ci/travis-ci/issues/1066

Since we currently don't have anything that would warrant continuing after a non-zero exit code, this solution is the simplest.

Closes #107
tkphd/pycalphad,tkphd/pycalphad,tkphd/pycalphad