tests: First test for gr.char function.

To run the tests simply call:
  python setup.py tests

Change-Id: I636f36150957e7c5a339585cf80d364c3fbc24ae
Reviewed-on: https://iffwww.iff.kfa-juelich.de/review/130
Reviewed-by: Christian Felder <c.felder@fz-juelich.de>
Reviewed-by: Josef Heinen <j.heinen@fz-juelich.de>
Allow GKS to be used in an EMSCRIPTEN environment

Change-Id: Ibd8b445b52a5bd04e04fcca1c290d8a2aa397947
Reviewed-on: https://iffwww.iff.kfa-juelich.de/review/131
Reviewed-by: Josef Heinen <j.heinen@fz-juelich.de>