isNumeric: Updated description based on new behavior

Fixes gh-817
Closes gh-819

Author: AurelioDeRosa

entries/jQuery.isNumeric.xml

@@ -9,7 +9,8 @@
     </argument>
   </signature>
   <longdesc>
-    <p>The <code>$.isNumeric()</code> method checks whether a value is a finite number, or would be cast to one by <code>Number</code>. If so, it returns <code>true</code>. Otherwise it returns <code>false</code>. The argument can be of any type.</p>
+    <p>The <code>$.isNumeric()</code> method checks whether its argument represents a numeric value. If so, it returns <code>true</code>. Otherwise it returns <code>false</code>. The argument can be of any type.</p>
+    <p>As of jQuery 3.0 <code>$.isNumeric()</code> returns <code>true</code> only if the argument is of type <a href="/Types/#Number"><code>number</code></a>, or if it's of type <code>string</code> and it can be coerced into finite numbers. In all other cases, it returns <code>false</code>.</p>
   </longdesc>
   <example>
     <desc>Sample return values of $.isNumeric with various inputs.</desc>