Optimizations (Parcel + CompositeDisposable + Disposable + Emitter)

[aminya]

Description of the change

This adds a couple of optimizations:

• Various optimizations in the CompositeDisposable, Disposable, and Emitter code
• Converts requires/module.exports to ES6 import/export
• Uses Parcel to bundle the code. ClosesEventKit now available on bower for browsers #33. FixesImplement UMD #35.

How to review

• Then follow the commit messages. Each commit is a very small change that you can review quickly.

Verification

All the tests pass. The changes are considered minor. They do not change the functionality.

[aminya]

@darangi@sadick254 Will you have time to take a look at these PRs? If not, since this package is an npm package, I can get access to the repository through the disputes procedure and continue maintaining it (similar to how we did for atom-languageclient).

[sadick254]

We plan on looking into the PR's we have here as well as on our other core packages.

[aminya]

@sadick254 I am just asking this to speed up the process. If you can offload the maintenance of some of the projects to the community, you will have more time focusing on the Atom's core. It is a Win-Win action.

As an example, since we have got atom-languageclient, we have updated it, so it has the latest features.
https://github.com/atom-ide-community/atom-languageclient