Allow to change context in a pjax:beforeReplace handler

Author: AntonTyutin

Diff for: jquery.pjax.js

@@ -281,14 +281,14 @@ function pjax(options) {
       state: pjax.state,
       previousState: previousState
     })
-    context.html(container.contents)
+    options.context.html(container.contents)
 
     // FF bug: Won't autofocus fields that are inserted via JS.
     // This behavior is incorrect. So if theres no current focus, autofocus
     // the last field.
     //
     // http://www.w3.org/html/wg/drafts/html/master/forms.html
-    var autofocusEl = context.find('input[autofocus], textarea[autofocus]').last()[0]
+    var autofocusEl = options.context.find('input[autofocus], textarea[autofocus]').last()[0]
     if (autofocusEl && document.activeElement !== autofocusEl) {
       autofocusEl.focus();
     }