[Agnostic] Switch encode() to allow double encoding

The use case is when you are storing HTML in a database that has some markup (like < >) but also some entities (&amp;).  I want to render the HTML exactly how it is in the database but currently the entities get decoded when they get rendered into a Former form field
Merge pull request #204 from weotch/develop

[Agnostic] Switch encode() to allow double encoding