added posix mixin
added posix mixin

jonashaag/jedi,mfussenegger/jedi,flurischt/jedi,dwillmer/jedi,dwillmer/jedi,tjwei/jedi,mfussenegger/jedi,jonashaag/jedi,WoLpH/jedi,flurischt/jedi,tjwei/jedi,WoLpH/jedi