Tiller credentials persisted across "helm tiller start" sessions

[jonerer]

Thanks for a great plugin!

Our usecase is like this:

(set credentials for AWS role)
$ helm tiller start
$....
$ (Ctrl-D)

(set credentials for other AWS role)
$ helm tiller start
$...
$ (Ctrl-D)

But this doesn't really work currently since the first tiller session will be re-used by the second "start" command, unless I run a "helm tiller stop" between them. I think it would better if the tiller session was tied to the shell session that "start" starts.

I saw this also mentioned in #33