fixed error when the course id did not exist

until now whenever you tried to add members to a course that didn't
exist it just crashed, fixed it for now.
set password on confirmation. closes #37, should merge

this commit does a lot of stuff, but short story is this: upon
clicking the confirmation link it prompts the user with a form to
setup their password.
Merge pull request #39 from rcsole/one-time-password

One time password