Working directories are now set seperately from the commands so they
can later be swapped out when running linters over projects is
supported, and also better support filename mapping for running linters
on other machines in future.
Certain tests could break if you ran them separately from other tests.
They have been patched.
`run-tests` now has a `--fast` option which runs tests with only the
fastest Vim version ALE tests with, and the custom checks.
