Travis CI: initial release of configuration

• Forward-ported from 5b6225743b2f74344053f33dc70562675d360a3d so that there is no need to wait for the following big master-to-next merge in order to have working Travis CI configuration in the next branch.

• NOTE Removes regression testing part which is not yet next ready.

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>