WA-238 Safe Txs Frontend

[apanizo]

Description
This PR allows to create tx and get them ready to be confirmed. If the safe has only one owner, the transaction is executed straight away.

This PR includes a DOM test simulating the second case: 1 safe with one owner and add a multisig tx and featured tests for new selectors created.

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Known bugs

• Not creator owner can not operate with safe

Select account A in Metamask
Reload the connection in react-app
User A creates a new Safe with 3 owners (including user B and C as owners)
User A can see the new Safe in the list and can operate with it

Select account Z in Metamask
Reload the connection in react-app
User Z cannot see the new Safe in the list and cannot open it or operate with it

Select account B or C in Metamask
Reload the connection in react-app
User B/C can see the new Safe in the list but cannot open it or operate with it

• Remove google font and load it locally
• Check tx status '0x00 0x01' in testnets exception is nor raised
  https://github.com/ethereum/wiki/wiki/JavaScript-API#web3ethgettransactionreceipt

[apanizo]

Travis automatic deployment:
https://staging-30-pr-182-safe-react-gnosis.surge.sh

Storybook book automatic deployment:
https://storybook-staging-30-pr-182-safe-react-gnosis.surge.sh