Add angular directive "server-error"
Change username to email
When the login endpoint returns a 4xx error, return the data

This way that data can be used by anything calling the login, so we can
get back a list of errors.
The form now has error messaging

When the server returns an error, we can display it on the form!
Remove the footer logo/links
Add some more comments to the index.mako
Add new img static path
If the request body is set, but it is not JSON return 422
Return the actual user's email, rather than static variable
Remove debugging code
Add a new UserSchema that validates the login JSON
Validate the login JSON with the new schema

If the schema doesn't validate, we can return the errors back to the
client which can then use it on the front-end to display the error to
the user.
Add colander as a dependency