Version 1.1.0: getblocktemplate Support

This release focused on supporting the getblocktemplate call proposed in
BIP 22 and BIP 23 and implemented by Bitcoin Core and btcd. This finally allows
mining without a pool if you supply an address to mine coins to at the command
line.

HTTP work sources now default to using getblocktemplate instead of getwork.
This feature is new and might have bugs that could lead to loss of potential
mining rewards.

It looks like the work sourcing threads run into i/o issues occasionally due to
using the not-thread-safe Python http lib. I don't aim to address this as most
of the threaded communication ought to be completely replaced by an event runner
like asyncio or trio at some point.

Thanks to @momchil for the original getwork code, @luke-jr @sipa and @vsergeev
for helping me understand getblocktemplate.