Do an early exit if something breaks

[Luzifer]

As a coder automating my builds I want to use the golang-builder inside my Makefile or other automation to build my assets in a clean way. If the build isn't successful I want to stop the whole process in order not to do broken deployments.

This is achieved in this commit using #!/bin/bash -e which will ensure bash exits if any exit code is different than 0 and exit the build process with a non-zero exit code.

[bdehamer]

Looks like a good addition. Thanks.