Change User form to use Update for button if action is edit

I am also a new rails developer and I wanted to try a pull request. I noticed a small bug on your site. The user form for editing a profile still says "Join" even if you are already signed up. I Changed it to say "Update" if the user is editing the profile.

Please ignore if you are uninterested in this request and thanks for putting your code up on github.
Interesting. I did not know about that. Thanks for the info!