added ClientUtils.echo()

To print stuff out to the casper console from the remote page DOM environment:

```javascript
casper.start('http://foo.ner/').thenEvaluate(function() {
    __utils__.echo('plop'); // this will be printed to your shell at runtime
});
```

@@ -1782,10 +1782,18 @@ function createPage(casper) {
         return casper.filter('page.confirm', message) || true;
     };
     page.onConsoleMessage = function onConsoleMessage(msg) {
-        var level = "info", test = /^\[casper:(\w+)\]\s?(.*)/.exec(msg);
-        if (test && test.length === 3) {
-            level = test[1];
-            msg = test[2];
+        // client utils log messages
+        var level = "info", logTest = /^\[casper:(\w+)\]\s?(.*)/.exec(msg);
+        if (logTest && logTest.length === 3) {
+            level = logTest[1];
+            msg = logTest[2];
+            return; // don't trigger remote.message event for these
+        }
+        // client utils casper console message
+        var consoleTest = /^\[casper\.echo\]\s?(.*)/.exec(msg);
+        if (consoleTest && consoleTest.length === 2) {
+            casper.echo(consoleTest[1]);
+            return; // don't trigger remote.message event for these
         }
         casper.log(msg, level, "remote");
         casper.emit('remote.message', msg);

@@ -117,6 +117,16 @@
         };
 
         /**
+         * Echoes something to casper console.
+         *
+         * @param  String  message
+         * @return
+         */
+        this.echo = function echo(message) {
+            console.log("[casper.echo] " + message);
+        };
+
+        /**
          * Base64 encodes a string, even binary ones. Succeeds where
          * window.btoa() fails.
          *