code: function isGoodHash (hash, target) {
    hash = new Buffer(hash, 'hex')
    target = new Buffer(target, 'hex')
  
    return _.range(32).some(function (index) {
      return hash[index] < target[index]
    })
  }
docs: Check that given `hash` lower than `target`
  
  @param {string} hash
  @param {string} target
  @return {Boolean}