Docs & deps update

Improving docs.
Updating dependencies.

By default populate content-length if missing

v1.2.0

Merge pull request #3 from jkyberneees/populate-content-length-if-mis…

Updating fast-proxy dep

v1.1.2

updating "fast-proxy": "^1.1.2"

Dependency updates

Updating deps.

Gateway level cache

Supporting gateway level cache:

// cache middleware
const cache = require('http-cache-middleware')()
// enable http cache middleware
const gateway = require('fast-gateway')
const server = gateway({
  middlewares: [cache],
  routes: [...]
})