Upgrade and unpin devDependencies (ethjs#16)

* remove lint:staged script
* devDeps: remove unused eventsource-polyfill
* devDeps: [email protected]>^5.2.1
* devDeps: [email protected]>^9.1.2
* devDeps: [email protected]>^3.0.2
* devDeps: [email protected]>^7.2.0
* devDeps: [email protected]>^4.3.10
* devDeps: [email protected]>^1.2.2
* devDeps: unpin all remaining
* npm dedupe; npm audit fix

Author: legobeat