Support input event in addition to change event

[cyberixae]

The onChange callback used by the currency text field is a bit problematic because of the vague guarantees it provides of being called. I'm experiencing a problem with Chrome on Android where the the callback is ~always called with outdated data because according to specification the event doesn't need to fire every time something changes. It would be nice if CurrencyTextField would also support the onInput callback that is guaranteed to be called every time the user modifies the value.