Suppress warnings caused by deprecated method. 

On starting up JRuby Interpreter ([Plugins > Scripting > JRuby Interpreter]), Many lines of warning message appears. I replaced the method accordingly and they are now gone. 

```
Starting JRuby ...
done.
include_class is deprecated. Use java_import.
include_class is deprecated. Use java_import.
include_class is deprecated. Use java_import.
include_class is deprecated. Use java_import.
include_class is deprecated. Use java_import.
include_class is deprecated. Use java_import.
include_class is deprecated. Use java_import.
include_class is deprecated. Use java_import.
include_class is deprecated. Use java_import.
include_class is deprecated. Use java_import.
...
```