This is based mostly on: https://github.com/jupyter-widgets/ipyleaflet

…/testing

- drop homepage code
- drop quick server
- deprecate local_host, js_source, and static site options
- drop map / model cache

- in Python Builder, map_json and map_name can be set either when creating the
  instance or by modifying the attributes later
- The first_load_callback now takes a single builder argument to deal with the
  challenges in #187

…search closes

…alue

…esize