function capitalize(subject, restToLower) {
    var subjectString = coerceToString(subject);
    var restToLowerCaseBoolean = coerceToBoolean(restToLower);

    if (subjectString === '') {
      return '';
    }

    if (restToLowerCaseBoolean) {
      subjectString = subjectString.toLowerCase();
    }

    return subjectString.substr(0, 1).toUpperCase() + subjectString.substr(1);
  }
Converts the first character of `subject` to upper case. If `restToLower` is `true`, convert the rest of
`subject` to lower case.

@function capitalize
@static
@since 1.0.0
@memberOf Case
@param  {string}  [subject='']        The string to capitalize.
@param  {boolean} [restToLower=false] Convert the rest of `subject` to lower case.
@return {string}                      Returns the capitalized string.
@example
v.capitalize('apple');
// => 'Apple'

v.capitalize('aPPle', true);
// => 'Apple'