Create and release a certifier binary

[LucasRoesler]

It would be really great to have versioned binaries that we can then use in CI systems instead of needing to clone and run this repo. Having a built binary means we also don't need to worry about the go environment the user has.

we can use

go test -c ./tests -o faas-certifier

and this will produce a binary called faas-certifier for the tests.

[alexellis]

Please feel free to add a .travis.yml file for this and to add to the Trello board for tracking.