Pin dependency to sim_launcher to 0.4.13

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.

This is a temporary fix.  We will either remove the sim_launcher dependency (planned) or monkey patch.

Woot!  Thanks @moredip for releasing 0.4.13 to help us work around this issue.