Display error page when web3 is not available.

[richard-ramos]

An error page should be displayed under the following conditions:

1. No web3 provider available.
2. Connected to different network
3. Undhandled errors returned by Embark.

See teller network and voting dapp for inspiration on how we implemented that functionality:

• https://github.com/status-im/status-teller-network/blob/e09ee88dd621fc80beaef0cb144e2a7756826022/src/js/layout/App.jsx#L73
• https://github.com/status-im/status-teller-network/blob/master/src/js/services/embarkjs.js
• https://github.com/status-im/snt-voting/blob/f390765c24a5b2d383c2f515e6750e90af2c2dd0/app/dapp.js#L271
  https://github.com/status-im/snt-voting/blob/f390765c24a5b2d383c2f515e6750e90af2c2dd0/app/dapp.js#L284

[cryptowanderer]

This is not quite accurate. I want the page to load normally, no matter whether you have a web3 browser or not.

Errors should only be displayed when the user tries to do something that requires a wallet, i.e. "Submit a DApp" or vote.

[iamonuwa]

A notification div should always be in place. But the page should load normally. Errors should be displayed when you attempt to perform an action that requires web3