[Add] travis: add osx build
[Add] travis: add osx build

msincenselee/vnpy,msincenselee/vnpy,andrewchenshx/vnpy,bigdig/vnpy,bigdig/vnpy,vnpy/vnpy,vnpy/vnpy,bigdig/vnpy,andrewchenshx/vnpy,andrewchenshx/vnpy,andrewchenshx/vnpy,msincenselee/vnpy,msincenselee/vnpy,andrewchenshx/vnpy,bigdig/vnpy