Improve homepage

[patcon]

The homepage is now easier to edit, as it comes from a mustache template.

Also, it's prettier, with bootstrap properly in place.

Most importantly, it links to GitHub repo, which the front page of all our EDGI helper projects should.

[patcon]

ok, so improved the README:

• sync'd the halpy bot name between repo and live.
• made the mention of local viewing more explicit (which port on localhost)
• pointed to where halpy lives
• renamed repo to edgi-hubot-halpy for clarity

[patcon]

I haven't change the substance, and this has been in limbo forever, so going to merge :grimacing: