function replace() {
	      var args = arguments,
	          string = toString(args[0]);
	
	      return args.length < 3 ? string : string.replace(args[1], args[2]);
	    }
Converts `string` to
[snake case](https://en.wikipedia.org/wiki/Snake_case).

@static
@memberOf _
@since 3.0.0
@category String
@param {string} [string=''] The string to convert.
@returns {string} Returns the snake cased string.
@example

_.snakeCase('Foo Bar');
// => 'foo_bar'

_.snakeCase('fooBar');
// => 'foo_bar'

_.snakeCase('--FOO-BAR--');
// => 'foo_bar'