instead default to activate dune-common's

refs #30

this builds and runs tests w/o ctest first. Errors here will and should
fail our travis build as such. Afterwards ctest is run again on a
cleaned build dir. This should replicate results and submit those to
cdash, while enabling us not to have the travis build fail due to ctest
itself failing.

This reverts commit ba71a7857d78f85ff258834f7820928c253102af
since the update required cmake stuff in common (>=2.4)

* ensure dune-commons cmake stuff is used only with --use-cmake