QUGC-123 Use client#valid? since it has been refactored to check everything.
Merge branch 'master' into develop
add abstract loader that uses node.
add Superset#to_qdf
move require statements into respective files.
add Abstract.load for loading entire file into memory
refactor Node to Abstract::Node. Abstract uses self::Node. Superset defines Superset::Node which inherits Abstract::Node.
to_qdf uses superset node syntax. node close will only call block if there are lines to process
to_qdf returns nil if the object is invalid.
Merge branch 'develop'