Exiting on bad grunt exit code.
Merge pull request #13 from Banno/grunt-error-exiting

Exiting on bad grunt exit code.
Bumping next version to 1.3.15.
Merge branch 'sbt-13' into 1.4.x
Merge branch '1.4.x' of github.com:Banno/banno-sbt-plugin into 1.4.x