Request/response struct fields must still be exported, but deeper fields
in them can now be unexported. This allows the use of types such as
big.Int which contains unexported fields.

Object.ImplementsJSONMarshaler=true if it has a custom marshal method
(MarshalJSON or MarshalText).

This indicates to non-Go clients the need for special handling of the
object (usually parsing it).

Use text/template if file extension = ".tmpl".

Note: Template functions returning template.HTML doesn't seem to cause
trouble? Leave for backward compatiblity.