Merge pull request #18 from sourcegraph/tickets

perm grant ticket authenticated transport
DefFormatStrings and Def.FmtStrings
Merge pull request #20 from sourcegraph/def-format

DefFormatStrings and Def.FmtStrings
BuildsService.DequeueNext and associated route
auth ticket transport
return resp
treat a Builds.DequeueNext 404 as a non-error (just a nil build returned)
nil check