ensured travis-ci is able to run the tests using phantomjs 1.5

-var received;
+// skip this test for phantom versions < 1.5
+if (phantom.version.major === 1 && phantom.version.minor < 6) {
+    casper.test.comment('Skipped tests, PhantomJS 1.6 required');
+    casper.test.done();
+} else {
+    var received;
 
-casper.setFilter('page.confirm', function(message) {
+    casper.setFilter('page.confirm', function(message) {
         received = message;
         return true;
-});
+    });
 
-casper.start('tests/site/confirm.html', function() {
+    casper.start('tests/site/confirm.html', function() {
         this.test.assert(this.getGlobal('confirmed'), 'confirmation received');
-});
+    });
 
-casper.run(function() {
+    casper.run(function() {
         this.test.assertEquals(received, 'are you sure?', 'confirmation message is ok');
         this.test.done();
-});
+    });
+}

-casper.setFilter('page.prompt', function(message, value) {
+// skip this test for phantom versions < 1.5
+if (phantom.version.major === 1 && phantom.version.minor < 6) {
+    casper.test.comment('Skipped tests, PhantomJS 1.6 required');
+    casper.test.done();
+} else {
+    casper.setFilter('page.prompt', function(message, value) {
         return 'Chuck ' + value;
-});
+    });
 
-casper.start('tests/site/prompt.html', function() {
+    casper.start('tests/site/prompt.html', function() {
         this.test.assertEquals(this.getGlobal('name'), 'Chuck Norris', 'prompted value has been received');
-});
+    });
 
-casper.run(function() {
+    casper.run(function() {
         this.test.done();
-});
+    });
+}