Massive first pass at making code arc-compatible.

This also starts the process of getting the XCode project
building again. That said, while XCode successfully builds
the binary, it won't run. And the makefile isn't building
successfully yet. More to come.
Drop _selector in ViTaskRunner.

We've changed ViTaskRunner to always invoke the same
selector on its target. Targets should use contextInfo to
disambiguate between multiple possible callback targets.

The change was already implemented, but there was still a
vestigial _selector instance variable in the ViTaskRunner
class.
Expose stderrString from ViTaskRunner.
Add debug print of filter output on failed run.
Centralize task runner callback handling in ViTextView.

contextInfo is now always a dictionary with a type key. The
@"type" key is used to decide which callback to use. To
avoid warnings, we have a protocol with the two methods
that the bundle_commands and vi_commands categories
define as callbacks for the task runner marked as optional.
Drop OS-specific log targeting for SFBCrashReporter.

Since we're targeting OS X 10.8+, we don't need to
accommodate Leopard-.
Switch to SBJsonParser 3.2.

This lets us use ARC on SBJsonParser, as well.
Fix crash reporter to use NSFileManager for trashing crash reports.
Couple of miscellaneous ARC- and 10.8-related fixes.