Merge pull request #41 from cryptocrack/fix-offline-status

Add offline status
Oops I forgot to merge this, sorry!
wa_api.cc: Add explicit type casts

We need to cast C strings to std::string before passing them to the
WhatsApp protocol engine. Add missing explicit casts.

Signed-off-by: Lukas Fleischer <info@cryptocrack.de>
Use proper default resource

Use a proper default resource instead of misusing the user agent string
as a resource string. The default value is taken from the yowsup
sources. This hopefully fixes issue #37.

Signed-off-by: Lukas Fleischer <info@cryptocrack.de>