Refactore index.js to be able to be required programmatically

[92bondstreet]

What?

This MR contains largely a smooth refactoring to use gcal-cli also in a programmatically way.

How?

• add the bin entry point bin.js
• move google apis method to api.js
• expose client, api and core method from index.js
• add Do directives doc for the first authorization installation
• settle bulk promises instead of call them with Promise.all

[toniov]

Thanks for the PR! It's a huge refactor so let me take a close look at it :) I think it's big enough to be released as an upgraded major version.

Btw what do you mean by dynamic way? Exposing the methods to be able to be required programmatically?

[92bondstreet]

I edited also the description and the MR title to be explicit about the programmatically way.

[92bondstreet]

The next step will be to upgrade dependencies and move googleapis from v21 to v33

[92bondstreet]

Regarding all refactoring and new features, we could also open the PR to a dedicated branch.

[toniov]

Regarding all refactoring and new features, we could also open the PR to a dedicated branch.

Since this is quite big I think that's a good idea! We could separate it in several PRs to a dedicated branch, and at the end merge that branch with master in a final PR.

[toniov]

I created a branch called 2.0.0.

This order could be nice, so we can isolate possible bugs:

1. Architecture refactor (splitting files and so on, not changing code)
2. Code refactor (e.g. changing Promise.all() with pSettle)
3. Upgrading dependencies
4. New functionality (e.g. enable?)