JavaScript seedable random number generator

The generator below, seeded with "Example" will produce the same
values as below for each of these random number distributions across
all browsers.

``javascript
var rng = new RNG('Example');
rng.random(40, 50); // => 42
rng.uniform(); // => 0.7972798995050903
rng.normal(); // => -0.6698504543216376
rng.exponential(); // => 1.0547367609131555
rng.poisson(4); // => 2
rng.gamma(4); // => 2.781724687386858
`

The underlying algorithm is RC4 and uniform number generation is about
10x slower than Math.random in V8. What you get in exchange for that
is a seedable generator and additional random distributions (see
example). You can still get speed and these additional distributions
by using Math.random as the core uniform number generator.

`javascript
var rng = new RNG(Math.random);
`

When no seed is provided, one is created randomly from available
entropy sources. Seeds that are not strings are run through
JSON.stringify() before being used.

Here's how you would replace Math.random with a seeded generator.

`javascript
Math.random = RNG.prototype.uniform.bind(new RNG('my seed'));
`

Finally, for fun, a dice roller,

`javascript
var dice = RNG.roller('4d6 + 10');
dice(); // => 17
dice(); // => 11
`

Node.js Usage

`javascript
var RNG = require('rng');
``

This module can also be [browserified][browserify] thanks to
[browserify-shim][shim].


[browserify]: https://github.com/substack/node-browserify
[shim]: https://github.com/thlorenz/browserify-shim