Update salt bootstrap tutorial to fix instances of 'install_salt.sh.sh'

[gravyboat]

This ties into saltstack/salt-bootstrap#465, but it looks like when I copied over some of the commands into the bootstrap tutorial (http://docs.saltstack.com/en/latest/topics/tutorials/salt_bootstrap.html) I missed the fact that there were a few occurrences of '.sh.sh' for the commands. That should be fixed.

[rallytime]

Good catch! Thanks for the report @gravyboat! :)

[s0undt3ch]

I think the cleanest way to keep this in sync is to start documenting the bootstrap script with sphinx and link the docs...

[gravyboat]

@s0undt3ch That works for me, an update to the readme just linking over would be simple. It would be good to double check and ensure that all of the latest changes have made it into the bootstrap documentation file.