show usd balance under eth token balance

TODO:

* show usd amount in txForm Field
* show usd txCost in txForm Field
latest
Name Stage Failure
failed
linux-test Test
$ yarn test
yarn run v1.22.5
$ semistandard '**/*.{js,ts}' --parser babel-eslint && CI=true lerna run test --parallel
semistandard: Semicolons For All! (https://github.com/Flet/semistandard)
/builds/parity/fether/packages/fether-react/src/utils/estimateUsd.js:6:10: 'fetch' is not defined.
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
Cleaning up file based variables
ERROR: Job failed: exit code 1