Pin dependency to sim_launcher to 0.4.11

sim_launcher 0.4.12 removed the bundled ios-sim because it was
broken in Xcode 6 environments.  Unfortunately, this requires
calabash users to install ios-sim or see runtime exceptions even
if they are not directly using ios-sim.
Use 0.4.13 sim_launcher; includes ios-sim binary
Merge pull request #580 from calabash/feature/rollback-sim-launcher-dependency

Pin dependency to sim_launcher to 0.4.13