Drop obsolete connect-livereload middleware.

With assemble, we can get rid of the connect-livereload middleware.

– Insert the livereload using assemble based on new custom variable
  'remote' (is set to true if generating HTML for deployment).
- Add new task 'assemble:dev' for generating local files.
- Remove obsolete middleware Grunt plugin.
- Rewrite 'copy' task since HTML generated for deployment is now
  generated directly into 'dist/'.