Create gomemcached + goxdcr MH branches

There are two repositories that are part of the XDCR repo: goxdcr and gomemcached .

We would like to follow suit and make mad-hatter branches in both, so that the master branches in both repositories can move forward with CC dev.

So this MB tasks is to ask for help in the following:

1. Create MH branch for goxdcr with 4737497385679f04ff03f7a5a2df7cb4e7c6d2b6 as the tip.
2. Create MH branch for gomemcached with 2b4197fedf38f694a33465050d1396e03e97db19 as the tip.
3. For Mad-Hatter manifest, point to the above branches instead of master as it is now.
4. Bonus: If there is a way, could we add a hook to gomemcached gerrit somehow so that if people who check fixes that could apply to mad-hatter into master, that they will know to backport it to the mad-hatter branch?