Add CardGenerator unit test

Added a first unit test for the CardGenerator class. It currently only contains
one test case for generating a virtual nPA.

In order to use this test some changes to the TravisCI configuration are
required. Especially the OpenPACE python bindings need to be build before
vsmartcard is being tested since the vsmartcard nPA functions use these
bindings.
Merge pull request #34 from d0/master

Add CardGenerator unit test