Updated travis config file to use conda

[tpaviot]

This branch:

• adds a conda build script
• uses conda to build smesh on travis
• adds support for both osx and linux on travis

[tpaviot]

@jf--- yes maybe. I did not find any other solution/place to run make test

[jf---]

i tried a few things:

• binary_relocation off -> on
• set MACOSX_RPATH to $PREFIX/lib
• run make install before make test

conda creates another env for tests, while gtests are ran in the build env i'm pretty confident this is the source of error

but no idea how the test could be invoked separately