function isRegExp(value) {
    return toString.call(value) == regexpClass;
  }
Checks if `value` is a regular expression.

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

_.isRegExp(/moe/);
// => true