index.js
function obv (fn, immediate) {
    if(!fn) return state
    listeners.push(fn)
    if(immediate !== false && fn(state) === true) obv.more()
    return function () {
      var i = listeners.indexOf(fn)
      listeners.splice(i, 1)
    }
  }
function obv (fn, immediate) {
    if(!fn) return state
    listeners.push(fn)
    if(immediate !== false && fn(state) === true) obv.more()
    return function () {
      var i = listeners.indexOf(fn)
      listeners.splice(i, 1)
    }
  }
function obv ( fn , immediate ) { if ( ! fn ) return state listeners . push ( fn ) if ( immediate !== false && fn ( state ) === true ) obv . more ( ) return function ( ) { var i = listeners . indexOf ( fn ) listeners . splice ( i , 1 ) } }
implement an observable
implement an observable