function isBoolean(value) {
    return value === true || value === false || toString.call(value) == boolClass;
  }
Checks if `value` is a boolean (`true` or `false`) value.

@static
@memberOf _
@category Objects
@param {Mixed} value The value to check.
@returns {Boolean} Returns `true` if the `value` is a boolean value, else `false`.
@example

_.isBoolean(null);
// => false