Kickstart openzeppelin js

[spalladino]

Design the initial contents for openzeppelin js.

• Wrap GSN web3 provider to have transparent metatx support
• Allow to easily create web3 contract instances given the proxies deployed via zos (in both development in production, so we may not be able to leverage the hot-loader for this)
• Provide an easy way for starting and loading the web3 instance. Include the usual web3 intialization code (load metamask instance and enable it, or fall back to an infura node).
• Include React-based components (similar to redux's Provider, hooks, or connect) for simplifying access to the web3 instance of any of the contracts.

[ylv-io]

Workflowy with more details.

[spalladino]

Clearly done https://github.com/OpenZeppelin/openzeppelin-network.js