static compareTokens(first, second) {
    return second.nextReset - first.nextReset
  }
compareTokens

@param {module:core/token-pooling/token-pool~Token} first first token to compare
@param {module:core/token-pooling/token-pool~Token} second second token to compare
@returns {module:core/token-pooling/token-pool~Token} The token whose current rate allotment is expiring soonest.