Move code to AttributesParser so it can be reused

[sebastienbeau]

@did I need to reuse some code of the with_scope so I move it into AttributeParser

[did]

@did I need to reuse some code of the with_scope so I move it into AttributeParser

The evaluate_attributes method from the SimpleAttributesParser class (used to be called AttributesParser) has a different method signature AND it stores the results in the @attributes instance variable.

But the evaluate_attributes from the AttributesParser class(used by with_scope) doesn't do that.

And I'm concerned by the lax option and I don't think how it could act in the new evaluate_attributes method.