remove inferno (bug TBD)

Inferno is out of date, and is a duplicate for the package build system we have. We actually have three build systems now:

- inferno
- Makefile (```make package```)
- gulp 

[gulp](https://github.com/mozilla/fireplace/pull/753) will win out. And fabric already bumps the newest version of the package on dev.

There is also some updates to the README that had some outdated stuff. Though I am going to write complete frontend docs on sphinx.
I integrated it in the sections. It's very sparse and in-depth for any first looking at Fireplace and shouldn't be at the top of our README.