TwoDividerItemDecorator

Added a `TwoDividerItemDecorator` which provides 2 different dividers for horizontal and vertical layouts.
It works as the `DividerItemDecorator`.

Doc:
``` java
final Drawable dividerVertical = getResources().getDrawable(R.drawable.divider_vertical);
final Drawable dividerHorizontal = getResources().getDrawable(R.drawable.divider_horizontal);
mRecyclerView.addItemDecoration(new TwoDividerItemDecorator(dividerVertical,dividerHorizontal));
```

Sorry for pull request in master branch, but I've not found a dev branch.