[zcash/zcash] Help users understand “transaction not mined” situations (#1959)

@str4d, if you have some spare cycles, could you look at the text in this [google doc](https://docs.google.com/document/d/1Ducz4iNN3OEC5WwQkQRa1z7wh96AukZKgmjcA0N2SK0/edit?usp=sharing) and wordsmith it to be more accurate if you see fit? If you don’t respond, we’ll just go ahead with our wording.

This post was last modified on May 7, 2018, 11:07 pm