code: function isMergeable (val) {
    return val &&
      (typeof val === "object") &&
      !Array.isArray(val) &&
      !(val instanceof RegExp) &&
      !(val instanceof Date);
  }
docs: Determines whether the given value can be merged,
  or if it is a scalar value that should just override the target value.
  
  @param   {*}  val
  @returns {Boolean}