Stronger type checking

el.tagName returns a string, so better to check type and equality by changing '==' to '==='

Author: chiester

index.js

@@ -236,7 +236,7 @@
 
     function getSVGNode(el) {
       el = el.node()
-      if(el.tagName.toLowerCase() == 'svg')
+      if(el.tagName.toLowerCase() === 'svg')
         return el
 
       return el.ownerSVGElement
@@ -290,4 +290,4 @@
     return tip
   };
 
-}));
+}));