Changed the error report so it brings the user to Github directly

Making error reporting too easy results in too much context-less
tracebacks which demand attention and, in the end, aren't of much use.

Requiring the user to report errors on Github will reduce the number of
reports, but hopefully make these reports have better context.
Moved Cocoa error reporting to Github mode.
Bootstrapping: don't use system-site-packages under OS X
Update loc