field/form validation

[rafd]

For each model:

• make sure all fields are validated by RoR
• use a front-end validation solution, potentially make use of the tooltip library

[rafd]

Don't hate me, but, I think we should go with this gem:
https://github.com/bcardarella/client_side_validations

It automatically pulls in validations from the model.

[rafd]

Could you do the following to complete this issue:

• go through each model, and add validation methods where necessary (including the devise user forms)
• test that the forms still work and that the validations show

[fionatran]

Client-side validations work now for me (haven't pushed to github yet), although there are two minor issues:

• for the User signup and edit User, the error message appears 3 times (e.g. "is invalid is invalid is invalid" for email address)
• for edit Course, the error message is in black, even though the error message class (.field_with_errors .message) is red

[rafd]

push what you have, and add these issues as new issues