Upgraded node-jose and some development dependencies

Updated `node-jose` to version 2.0.0 to resolve security issues

Improved formatting
Updated documentation and added some comments

1.2.4 bumped version

* updated dependencies

* set type to commonjs
* restructured package
* moved index.js into src

* Updated dependencies

* Resolved security audit issues
* Ran prettier over docs
* Improved formatting

* updated dependencies

* renamed test files
* added clarifying docs
* reduce package size

Add encrypt options

No longer rely on 3rd party keyPair generator library.

Updated various development dependencies

Updated a number of devDependencies

Updated required node version to latest LTS
Removed npm version restriction