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
demo/index.html uses local annyang.js when launched from localhost

for development and testing purpose
Merge pull request #87 from PavelVanecek/feature-grunt-dev

New grunt task added by @PavelVanecek for easier development