Based on the latest changes to change notify(Selector) to notify(Object), updated the way headers are handled. Introduced a HeaderResolver abstraction that a Selector provides to a caller that is responsible for parsing the key object and returning any pertinent headers. The Dispatchers were then updated to accommodate this new pattern.

Also renamed Tagable to Taggable and updated references.
Ignore Structure101 files.
Change SelectorSpec to use the headers as the source of the resourceId to ensure that a test covers setting of headers from selector matches.