fixed Datetime & IP TOC links

Author: JacobWeisenburger

README.md

@@ -57,8 +57,8 @@
 - [Coercion for primitives](#coercion-for-primitives)
 - [Literals](#literals)
 - [Strings](#strings)
-  - [Datetime](#datetime-validation)
-  - [IP](#ip-address-validation)
+  - [Datetime](#iso-datetimes)
+  - [IP](#ip-addresses)
 - [Numbers](#numbers)
 - [BigInts](#bigints)
 - [NaNs](#nans)