fix(client): Allow leading/trailing whitespace on email addresses

@zaach - mind reviewing?

This is comprised of 2 commits, the first fixes the leading/trailing space on email problem, the second standardizes the parameter name for an element to `el` instead of a mix of `el`, `which` and `selector`.

fixes #519 
As @pdehaan reveals, we're now trimming emails at two spots. Whatever, but it's worth pondering.