* Export iso8601ToRippleTime(), txFlags, convertStringToHex()
* Fix a bug that caused fees exceeding 999 to throw an error
e.g. '1,000' would not be recognized as a valid number.
To use 6 decimal places, toFixed should be used instead of toFormat.
* Add maxFeeXRP (default 2 XRP) as an optional RippleAPI constructor parameter
- No calculated or specified fee can exceed this value
- If the fee exceeds 2 XRP, throw a ValidationError
* sign() - throw ValidationError when Fee exceeds maxFeeXRP
* Document getFee parameters
* Explain new fee limits in HISTORY.md
* Deprecate `maxFee`
