v2.2.0 - new major version for mempool-js (#2)

* - Refactoring code.
- Refactoring folder structure.
- Adding apiEndpoint and websocketEndpoint to Mempool config.
- Adding brownserify feature.
- Adding MIT LICENSE

* - Changing package.json information.
- Reorganizing README.md information.
- Default export for CommonJs and ES6 Modules.
- Changing default variable to mempoolJS.
- Organizing the API and WS providers.
- Splitting websocket connection types: client and server.

* Change version to 2.2.0.
Reorder keywords in alphabetical order.

.gitignore

@@ -1,3 +1,2 @@
 /node_modules
-.env
 /lib