added grunt dev command

usage:

     grunt dev

this will launch a web server on https://localhost:8443 using selfsigned certificate. This allows for nicer debugging and development, as you don't need to re-accept the popup everytime you reload the page.
added developing section to README
Improved README

Pages hosted on HTTPS do not need to ask repeatedly for permission, whereas HTTP hosted pages do.
Merge branch 'feature-grunt-dev'