Per commentary in b1330171be, move
away from mobc and standardize on deadpool.
This means that a couple of the newly added pool parameters
are no longer present, but nobody has had a chance to embrace
those yet anyway.
Make a note in the changelog about the recent changes: I fixed a bug
that no one had noticed before, which was that the username/password
parameters for single node redis were ignored. This was fixed by
52ca4d8be0
Remove the r2d2 dep (which is synchronous only) and replace with
mobc which is a bit easier to use, async, and seems more developed.
Update the interface to expose more of mobc's connection pool
options.
Add explicit redis cluster integration tests.
Wez Furlong