Use 'good fee' provider to provide users' effective fee rates

[jim618]

cointape.com provides estimates of the 'right' fee to use to get transactions confirmed.

There is an API here: http://www.cointape.com/api

This could be incorporated as a more advanced dynamic fee option i.e. Do you want a fixed fee rate or use a fee rate provider ? On the Fees dialog.

[gary-rowe]

We've received some user feedback from the community about incorporating this, especially in light of the ongoing "stress tests".

I propose we move this into 0.1.5. Because it relies on a third-party API provider we may need to consider multiple alternative feed providers (including ourselves) and also what to do in the absence of a provider.