function lowerCase(subject) {
    var subjectString = coerceToString(subject, '');
    return subjectString.toLowerCase();
  }
Converts the `subject` to lower case.

@function lowerCase
@static
@since 1.0.0
@memberOf Case
@param  {string} [subject=''] The string to convert to lower case.
@return {string}              Returns the lower case string.
@example
v.lowerCase('Green');
// => 'green'

v.lowerCase('BLUE');
// => 'blue'