Merge pull request eligrey#71 from minj/ff-addon-support

FF addon support

Author: eligrey

FileSaver.js

@@ -14,12 +14,14 @@
 
 var saveAs = saveAs
   // IE 10+ (native saveAs)
-  || (navigator.msSaveOrOpenBlob && navigator.msSaveOrOpenBlob.bind(navigator))
+  || (typeof navigator !== "undefined" &&
+      navigator.msSaveOrOpenBlob && navigator.msSaveOrOpenBlob.bind(navigator))
   // Everyone else
   || (function(view) {
 	"use strict";
 	// IE <10 is explicitly unsupported
-	if (/MSIE [1-9]\./.test(navigator.userAgent)) {
+	if (typeof navigator !== "undefined" &&
+	    /MSIE [1-9]\./.test(navigator.userAgent)) {
 		return;
 	}
 	var
@@ -228,6 +230,10 @@ var saveAs = saveAs
 		null;
 
 	view.addEventListener("unload", process_deletion_queue, false);
+	saveAs.unload = function() {
+		process_deletion_queue();
+		view.removeEventListener("unload", process_deletion_queue, false);
+	};
 	return saveAs;
 }(
 	   typeof self !== "undefined" && self