Add a module for Crashlytics

Maybe other services as well.

``` java
public class CrashlyticsLn extends DebugLn {

  public CrashlyticsLn(String packageName) {
    super(packageName, Log.VERBOSE);
  }

  @Override protected void println(int priority, String msg) {
    Crashlytics.log(msg);
  }
}
```
