Don't run in Safari

Summary: Safari has weird bugs associated with inline-table and
vertical-align, so we just won't render in Safari.

Auditors: alpert

katex.js

@@ -244,6 +244,10 @@ var clearNode = function(node) {
 };
 
 var process = function(toParse, baseNode) {
+    if (utils.isSafari) {
+        throw new ParseError("KaTeX doesn't work on Safari");
+    }
+
     clearNode(baseNode);
     var tree = parseTree(toParse);