Adding support for Martini & Goji frameworks - Go

Adding benchmark support for Martini & Goji, two web frameworks for Go.

See: 
   - http://martini.codegangsta.io
   - https://github.com/go-martini/martini
   - https://github.com/zenazn/goji
   - https://goji.io
@agrison In addition to alex's comment on `env=env`, I'll add that it's useless here. Your entire environment is persisted into the subprocess by default, including that snazzy GOPATH update above ;-) Please remove `env=env` from all of these subprocess lines