bump to v0.4.0 (openethereum#499)

Merge pull request openethereum#370 from paritytech/luke-misc-thibaut

Change Cancel to Back button. Password field autofocus on Unlock component

Merge pull request openethereum#259 from paritytech/am-fix-ci-2

Add default case

Merge pull request openethereum#241 from paritytech/ac-update-deps

Update @parity/electron dependency (fix openethereum#240)