travis - reduce the size of the test matrix
travis - reduce the size of the test matrix

This is a larger project and 8 separate build combinations didnt seem necessary,
and some builds were failing to clone the repo (possible throttling?).
Reduce the matrix to practical combinations. Release mode on osx+clang, and linux+gcc.

romeojulietthotel/LimeSuite,limemicro/lms7suite,myriadrf/LimeSuite,myriadrf/LimeSuite,limemicro/lms7suite,limemicro/lms7suite,limemicro/lms7suite,myriadrf/LimeSuite,romeojulietthotel/LimeSuite,romeojulietthotel/LimeSuite,limemicro/lms7suite,romeojulietthotel/LimeSuite,myriadrf/LimeSuite,romeojulietthotel/LimeSuite,myriadrf/LimeSuite