https://greenkeeper.io/

Travis-CI has become completely unusable for macOS testing, with builds
consistently taking over 2 hours to finish queueing.

Fix a potential issue with how the script was being executed before. It
was possible for the script streaming to break partway through being
passed to `sh`.

Remove macOS testing

As Atom initializes any service providers as part of package activation,
moving the requires in there wasn't actually saving us any time. Move
the initialization of these requires into an idle callback triggered
from the activate() call, and ensure they are ready before use.

This brings activation time from ~500 ms down to 10 ms. A further ~6 ms
can be shaved off by bringing the code from `config.js` into the main
file, but that will need updating/refactoring of the remark engine.

…-time

Defer dependency loading

Bring in `async` compatible versions of `beforeEach` and `it` from the
`jasmine-fix` module and refactor the code accordingly.

Async-ify the specs

If there are any pending idle callbacks registered by this package when
it is requested to be deactivated, then cancel them before they run.

Cancel pending idle callbacks on deactivate

If the package is deactivated, and then re-activated without restarting
Atom this could potentially cause issues as there would still be handles
stored from the previous activation.

If the idle callback hasn't triggered yet when a `lint()` is called,
immediately bring in the dependencies instead of waiting for that to
complete.

Minor fixes to callback handling