Update build process to use available development headers instead of included libraries.

I've done as discussed in https://github.com/galkahana/PDF-Writer/issues/15

---

This relies on the pkg-config support provided by cmake. This works after a fresh clone on my box (linux). I don't have a windows box to test the build on at the moment. I'll have one available tomorrow if there's a problem.

Same general process as before.

```sh
cmake .
make
```

For linux you'll need the development packages for libtiff, zlib, libjpeg, and freetype.

```sh
sudo apt-get install libtiff-dev zlib1g-dev libfreetype6-dev libjpeg-dev
```