EthProvider error handling

[dxnght]

• I'm submitting a ...
  [ ] bug report
  [x] feature request
  [ ] question about the decisions made in the repository
  [ ] question about how to use this project

• Summary

• Please, add handling for this error (after disconnection). And also it should be good if EthProvider could handle canceling of Metamask signing.

• Other information (e.g. detailed explanation, stacktraces, related issues, suggestions how to fix, links for us to have context, eg. StackOverflow, personal fork, etc.)