Merge branch 'master' of https://github.com/wwu-numerik/dune-stuff into dune-testtools

Conflicts:
	.travis.yml
	dune/stuff/test/grid_provider_cube.cc
	dune/stuff/test/grid_provider_dgf.cc
	dune/stuff/test/grid_provider_gmsh.cc

Resolved grid_provider files to local (deleted).
Resolved travis.yml to local except that it includes the new licence header now.