Add tsuru/golang PPA automatically

[turicas]

I think we can add the tsuru/golang PPA automatically on this script, since the Go version on Ubuntu is not updated enough to install tsuru CLIs using go get. We can add this line to the script:

            sudo apt-add-repository ppa:tsuru/golang -y >/dev/null 2>&1

[andrewsmedina]

The script already install the golang from tsuru ppa if the flag (--tsuru-from-source) to install tsuru from source is enabled: https://github.com/tsuru/now/blob/master/run.bash#L410

[turicas]

@andrewsmedina, if I don't install using --tsuru-from-source the machine will end up without this PPA so if I just want to update the tsuru CLI on the future I'll need to add the PPA and then install. The suggestion to always add the PPA is to have a more homogeneous final environment on the machine, no matter the options you've used.

[andrewsmedina]

I'm +1. I just added the link to the function that should be used to do it :)

[andrewsmedina]

@turicas you don't need the golang to update tsuru CLI. unless you wan't to install the CLI from source.