Bumped twitter-server to 1.6.1

We need (kinda urgently) Finagle 6.17+ to use new MySQL things, and also just because it's not good to be so behind in bugfixes and etc.

I've tested this patch with our internal applications, everything compiles and works fine.

//cc @fwbrasil @grandbora @folone @salomvary @codemanki