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
`subprocess.call()` waits command finished.
Use `Popen` instead.