Support Tiller install in alternate namespace

[NaomiReeves]

I have a use case where tiller is installed into a specific (not kube-system) namespace in my clusters. I'd like to be able to pass in a value to the helm init command with the --tiller-namespace flag so I can use this plugin. If the parameter is set, it would append to the init command.

[ipedrazas]

Done!

[NaomiReeves]

👍 works! Thank you!