Remove comment missed in #1525

Remove comment on using `nativeIndexOf`
Merge pull request #1553 from megawac/patch-1

Remove obsolete comment about using native indexOf
define _.contains for array-likes in terms of _.indexOf
Merge pull request #1556 from davidchambers/contains

define _.contains for array-likes in terms of _.indexOf
Avoid Function#call unless context is provided.

Fix #1554.
Merge pull request #1557 from braddunbar/iterator-context

Avoid Function#call unless context is provided.
Bail out early when appropriate.
Merge pull request #1559 from braddunbar/property-guard

Bail out early when appropriate.