Add workaround for travis issue.
Add workaround for travis issue.

As of the 2017-05-04 update to travis Precise images, /usr/local/bin/sbt is not
actually executable out of the box. We add a before_script hook per the
recommendation issued by the travis folks at travis-ci/travis-ci#7703 in order
to make sbt executable again, allowing the rest of the build to continue
normally.

lift/framework,lift/framework,lift/framework,lift/framework