Plug-in unable to load class

Error details:

```
Plug-in org.ganoro.phing.ui was unable to load class org.eclipse.ant.internal.ui.launchConfigurations.AntTabGroup.
org.eclipse.ant.internal.ui.launchConfigurations.AntTabGroup cannot be found by org.ganoro.phing.ui_1.0.0.201507041255
```

![2015-09-21_01-40_problem occurred](https://cloud.githubusercontent.com/assets/1009926/9983380/5701c674-6002-11e5-8c02-cf46cfa077fd.png)
