added eContents and eAllContents methods
tests for eContents and eAllContents
added setNilOrRemoveGeneric and setNilOrRemoveAllGeneric method
use eAllContents in ModelFragment
added disconnectContainer method
enforce unique containment rule, poped version to 0.7.0
testing setNilOrRemoveGeneric and setNilOrRemoveAllGeneric
fixed metamodel_from_ecore_tests not being run with minitest (Ruby 2.0)
added note about ELong support