Feature request: print a warning if you call `Form#submit` without specifying a `button` if there are multiple

[Nakilon]

Just spent an hour or more installing different debugging tools until found the cause of my error.

[flavorjones]

Hi @Nakilon, sorry you experienced this problem. Would you be interested in attempting to implement this in a pull request?

[weshatheleopard]

I think it can be handled by modifying Form#submit:

  def submit button = nil, headers = {}
+    warn "Multiple SUBMIT buttons available on the form." if submits.size > 1
    @mech.submit(self, button, headers)
  end

[flavorjones]

@weshatheleopard Thanks, I'd love a PR for this if you have the time and inclination.