no timeout, bundle install takes a while
Fix OS X issue in tests

@rjackson says that Dir.mktmpdir might not return the true path, so we
have to expand it.
Increase timeout

May help with CI issues
Prevent theoretical race conditions

They're theoretical because at the moment we're only supporting MRI,
which uses a GIL which means it's impossible for these data structures
to be simultaneously accessed.

However in the future we will support Rubinius, which has no GIL and may
need this synchronisation.
Disable test on 2.0.0-rc1 for now