[NOP] added support for travis-ci to OpenMS

 * for now we ignore AccurateMassSearch_test and GzipIfstream_test
[NOP] replaced echo 'yes' with the --yes flag of add-apt-repository
[NOP] re-enabled AccurateMassSearchEngine_test in travis-ci builds (see #669)
Merge pull request #668 from aiche/feature/travis-ci-support

[NOP] added support for travis-ci to OpenMS