* Remove `isEstimatedTxFee` since can just use `estimatedTxFee` to achieve same functionality

* Rename `newEstimatedTxFee` to `newGasEstimate` since it returns a value that's used for the `values.gas` prop

* Update `estimatedTxFee` to return `null` if the amount, gas, gasPrice values provided aren't valid, instead of returning the calculated estimated tx fee

* Wrap call to `estimateGas` in a try/catch block that throws error "Unable to estimate gas" when error thrown when calling `estimateGas` in TxForm.js

* Move check `if (!ethBalance) {` earlier in function

* Create TxDetails component and move relevant instance methods from TxForm into TxDetails

* Fix linting warning `Using target="_blank" without rel="noopener noreferrer" is a security risk: see https://mathiasbynens.github.io/rel-noopener`

* Remove isCancelled

* Remove estimatedTxFee from state

* Sort instance methods into alphabetical order

* Refactor by adding isEstimatedTxFee to check gas properties defined on form values

* Add instance method estimatedTxFee to return calculation based on gas values

* Move functions out of render function and change them into instance methods

* Remove duplicate check for whether values.gas existed

* Fixes error `Uncaught TypeError: Cannot read property 'resolve' of null at flush` that is generated after both valid amount and recipient values are entered

* Opens link to the Etherscan account page when the user clicks the TokenBalance component on the "Send Ether" page

* Opens link to directly to the specific token page of the Etherscan account when the user clicks the TokenBalance component on the "Send THIBCoin" (or other non-Ether token) page

* After entering a valid value and a recipient address, it works but the console displays error: `Uncaught TypeError: Cannot read property 'resolve' of null at flush (index.js:62)`

* On the 'Send THIBCoin' if you enter a valid value and a recipient address, the Tx Fee Estimate is shown as being the same value as the Amount, which is incorrect!