Use dynamic dispatch for sax_listener callbacks
Use dynamic dispatch for sax_listener callbacks

Instead of using case/when statements for all element names, use
a hash of {element_name: :element_logic_method} that maps element names
to instance methods with the relevant logic.

Use Sets instead of arrays since inclusion is the only check
performed.

Use Hash#key? instead of converting the keys to an array and checking
inclusion.

Also, did some tiny formating while per chance of a commit.

Many of these additions should be faster in theory.

All specs passing.

arxopia/risu,arxopia/risu,hammackj/risu,hammackj/risu