Restructure one-line config

[iamvery]

Currently, the lib is loaded on the client by require('phoenix_jank'), but this prevents using your own channel as proposed by #2. Would be nice to move things around something like:

option 1, zero config:

require("phoenix_jank/auto") // auto boots jank with "/jank" socket defined in lib

option 2, BYOC:

var Jank = require("phoenix_jank")
Jank.init("/your_socket") // any other options needed?