fix for #748 + tests for sympa.js
more elegant error handling when subscribing / unsubscribing from groups
Merge commit 'ec61e34802043b0153d289a58865c67cfad7bb36' into sympa-changes

Conflicts:
	package.json
Merge pull request #750 from leider/sympa-changes

fix for #748 + tests for sympa.js