Methods: Update email to use HTML5 regex, remove email2 method

The regex provided by the HTML5 spec allows email addresses without a top level
domain, like name@localhost. That makes the email2 method pointless.

Hopefully this is the last time the email methods ever has to be updated. At
least it will make bug triage easier: If you don't like the implementation,
report an issue against the HTML5 spec.

Fixes gh-828
Closes gh-753
Closes gh-739