Fix #7579. Don't convert to number if it changes the string. Close gh-852.

Net effect here is that hex numbers and most exponential-format numbers or long sequences of digits will remain strings rather than being coerced to numbers. `The people have spoken.

src/data.js

@@ -304,8 +304,9 @@ function dataAttr( elem, key, data ) {
 				data = data === "true" ? true :
 				data === "false" ? false :
 				data === "null" ? null :
-				jQuery.isNumeric( data ) ? +data :
-					rbrace.test( data ) ? jQuery.parseJSON( data ) :
+				// Only convert to a number if it doesn't change the string
+				+data + "" === data ? +data :
+				rbrace.test( data ) ? jQuery.parseJSON( data ) :
 					data;
 			} catch( e ) {}