<gold-email-input> is a single-line text field with Material Design styling
for entering an email address.
It may include an optional label, which by default is "Email".
<gold-email-input label="your email address"></gold-email-input>
The input can be automatically validated as the user is typing by using
required attributes. For manual validation, the
element also has a
validate() method, which returns the validity of the
input as well sets any appropriate error messages and styles.
Polymer.PaperInputBehavior for more API docs.
Polymer.PaperInputContainer for a list of custom properties used to
style this element.