Silent build failures in Travis CI

[95-martin-orion]

As seen on this build from PR #290, it appears that Travis will silently fail if the docker run command fails to build qFlex. Silent failures can potentially allow broken code to be submitted, so we need to fix this ASAP. Possible fixes:

• Enforce waiting for Travis checks prior to submit. (I thought we already did this, but stricter measures are apparently needed).
• Fix the docker run command to give a Travis-friendly error on build failure. (TBD: why is the current failure mode not Travis-friendly?)

Until this is resolved, please verify that all PRs show Travis checks as complete prior to submitting. Note that due to this bug, the "merge" button might be green without passing Travis checks! Please be careful.

[95-martin-orion]

Further discussion on #290 shows that even successful Travis runs do not show up.

@s-mandra, did we disable the Travis checks? I don't have access to the repo settings, but it should be in there (see this page for how to find it).

[s-mandra]

Let me take a closer look. Thanks for catching this!