renames node_list_sorting_test to node_list_insertion_sorting_test
implements NodeList merge_sort with tests
starts implementing engine
adds error checking for sort_function
must respond to call
added whitespace to NodeList for readability
added attr_accessor :previous :next to Entity
implements EntityList
adds whitespace for readability
updated to ruby 193

inserted ./ before all require calls - not sure what best practice is
but lets just get it working
implements create_component_hash in ComponentMatchingFamily
implements NodePool
renames instance var in Signals
adds NilComponentNodeError to Core module
extracts NodeIntrospector from ComponentMatchingFamily
implements ComponentMatchingFamily  new_entity method
implements ComponentMatchingFamily entity_removed method
completes ComponentMatchingFamily