Update .travis.yml (#87)
Update .travis.yml (#87)

nif building failed sometimes,  because erl_nif.h was missing -> install erlang-dev 
bump OSX version
scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris