added license file
Use as_json instead of to_json

ActiveSupport and the json gem both define things around to_json and interfere
in weird ways, causing custom to_json functions of hash values not to be called
add credits to modulefactory, they are mandatory
polish be_eql_after_json matcher a little
added modul_set constraint
update autotest file
added BA module in seed
test for fractional modul credits
use a decimal instead of an integer for the credits
more tests for studienplan
added .ruby-version
correctly instantiate subject in test
allow studiengang#moduls to be mass-assigned
use the initial_moduls from the studiengang if no modules were given