cleanups and adaptation to plugin API

- adding deprecation warning for old API
- making plugin API default in README and warning about deprecated old
  API
- adapted example to use new API and linked dependencies so no npm
  install is needed to run it
- renamed hack-prelude since it's no longer a hack
- upgrading browserify
- increasing peerdep browserify version range
- adding browerify-tool keyword
fixing .travis npm version and testing 0.8 and 0.10
minor readme fix
0.5.0 plugin API and proper prelude override
Update prelude based on newest version from substack/browser-pack
Fix support for browserify 5
Fix clientside tests to use plugin interface