travis: switch to other Boost PPA and test 1.53 and 1.55
stupidity...
travis: even more stupid...
travis: different repos for different versions

:-/
travis: enable APT caching and make tests more verbose
tests: advec: using different matcher
tests: stupid namespaces...
tests: on MPI run do not execute GTest::run() on all ranks

it is sufficient to run the tests only on the master node
tests: using another matcher

maybe this helps...
tests: mpi-fix for GTest

each MPI task should return the same test result; otherwise it might
happen that the test passed on rank 0 but one of the minor ranks finally
wins the race on returning from main
Merge branch 'development' into feature/travis-different-boost

Conflicts:
	.travis.yml
tests: further tweaking MPI advec test

errors of all ranks are checked and in case any rank fails, all will
fail;
Merge pull request #65 from torbjoernk/feature/travis-different-boost

travis: switch to other Boost PPA and test 1.53 and 1.55