replaceState() changed to pushState()

so that the "Back" button works after clicking on "Raw text".

js/zerobin.js

@@ -439,7 +439,7 @@ function stateExistingPaste() {
   */
 function rawText()
 {
-    history.replaceState(document.title, document.title, 'document.txt');
+    history.pushState(document.title, document.title, 'document.txt');
     var paste = $('div#cleartext').text();
     var newDoc = document.open('text/plain', 'replace');
     newDoc.write(paste);