Various fixes

* Fixed: if N and FN both existed, N was picked over FN even if it was empty. This closes #34 and cleans up the import mecanism for names.

* Fixed: N and FN are mandatory fields in vCard 3.0 (format we use for export). Partly fixes #19 
* Fixed: ADR field now properly exported (following vCard 3.0 standard). Other part of #19 fix.

I also took the chance the fix the travis build so it doesn't run tests again 0.8 anymore, but it runs them against 0.11 (allowed failure).

I noticed the build workflow wasn't the same than for other apps (like Files) so I changed it.