Merge branch 'release-0.2.0' into development
Silenced the rspecs, and capture stderr in shell.

closes #16
closes #18
Simpllify the build method of ShellTask.

No need for so many if statements, thanks CodeClimate!
Add test for the default configuration.
Add simple plugin system.

Well that was easier than expected (sort of, we picked ruby for a
reason after all).

closes #21
Merge branch 'add-plugin-system' into development
Bump the version number.
Merge branch 'release-0.3.0'