npm package

So I changed a lot here and am not sure if this is the direction you want to take the project...

Initially I wanted to clean up the build and get things setup to be on npm so it would work better with the browserify workflow as well as pave the way for a test+benchmark suite I am about to work on for opal.io (noticed problems in Safari 7.0)

A few keypoints:

* I named the npm package js-scrypt-em, published it and added you as an owner already: https://npmjs.org/package/js-scrypt-em
* Changes the interface to be a little more idiomatic; `scrypt` is the exported module and has a `scrypt.create(total_mem)` function for exposing the factory.
* Releases are now versioned in the browser directory
* Added package.json for npm/browserify
* builds an index.js for npm/browserify and then adds a UMD wrapper for the release in the browser dir
* Uses a mustache template instead of prefix and suffix files
* Fixes #3

My Makefile chops are probably not the smoothest and I am not super familiar with working with emscripten. The diff of my compiled version of srcypt was different than the one you have but I am assuming emscripten picks random var names etc.

Let me know if you want me to change anything. Thanks for making this available :)