fixed Casper#exists(), added Casper.Tester#assertExists() method

@@ -296,24 +296,14 @@
         },
 
         /**
-         * Exits phantom.
-         *
-         * @param  Number  status  Status
-         * @return Casper
-         */
-        exit: function(status) {
-            phantom.exit(status);
-            return this;
-        },
-
-        /**
          * Checks if an element matching the provided CSS3 selector exists in
          * current page DOM.
          *
+         * @param  String  selector  A CSS3 selector
          * @return Boolean
          */
         exists: function(selector) {
-            return self.evaluate(function() {
+            return this.evaluate(function() {
                 return __utils__.exists('%selector%');
             }, {
                 selector: selector
@@ -321,6 +311,17 @@
         },
 
         /**
+         * Exits phantom.
+         *
+         * @param  Number  status  Status
+         * @return Casper
+         */
+        exit: function(status) {
+            phantom.exit(status);
+            return this;
+        },
+
+        /**
          * Fills a form with provided field values.
          *
          * @param  String  selector  A CSS3 selector to the target form to fill
@@ -983,6 +984,19 @@
         };
 
         /**
+         * Asserts that an element matching the provided CSS3 selector exists in
+         * remote DOM.
+         *
+         * @param  String   selector   CSS3 selectore
+         * @param  String   message    Test description
+         */
+        this.assertExists = function(selector, message) {
+            var f = casper.exists(selector)
+            console.log('plop')
+            return this.assert(casper.exists(selector), message);
+        };
+
+        /**
          * Asserts that a provided string matches a provided RegExp pattern.
          *
          * @param  String   subject    The string to test