Fix #68.

Switch was using the relaunch mechanism built into Sparkle, which changed between the current shipping binary and the top of master, which Switch started using in 0.0.7. This ultimately meant I traded a corrupted code signature for a crash on the very first launch. Oops.

Switch now includes its own relaunch mechanism, which is a (minor) rewrite of Sparkle's old relauncher.
DOWN WITH TABS
Style/consistency fixes.
Better error checking in app delegate, hopefully last of style feedback in review.
Merge pull request #69 from numist/numist/68

Fix #68.