code: function asPromise (fn) {
    return new Promise((resolve, reject) => {
      fn((err, result) => {
        if (err) {
          return reject(err)
        }
        resolve(result)
      })
    })
  }
docs: Return a promise for a functon with node-style callback
  Usage:
  
  ```
  asPromise((callback) => fs.readFile('name', callback))
  ``
  `
  @param {function(callback:function(Error, any))} fn the function to generate the promise from
  @returns {Promise<any>}