add OSX support for travis-ci
add OSX support for travis-ci

- configure requires sed
- the python3 target uses rmdir with linux specific flags
- the c++ target hardcodes the brew bash path on OSX

scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris