Newline characters may be necessary for text that substituted by 'INCLUDE' pragma

Suppose the following text file (docs/*.txt):

```
INCLUDE: _foo

INCLUDE: _bar


```

Now, after substitution:

```
included foo.included bar.
```

This causes the following result.

![include002](https://cloud.githubusercontent.com/assets/1905688/2917291/2aef6f82-d6c4-11e3-877d-45bc7190e4a2.jpg)

The expectation that I think of is:

```
included foo.

included bar.


```