Ignore auto-generated files + check libraries

The outputs from autotools (`configure`, `Makefile.in`, `Makefile`, etc) should not be versioned. I have cleaned them up, added a `.gitignore` as well as the `autogen.sh` file so that the project looks like the one found on the [old SVN repo](https://svn.enlightenment.org/svn/e/OLD/epeg/). In addition I have added a check for required libraries which comes in handy e.g if libexif (which is now required) is not installed.

Thanks to [Github Release](https://help.github.com/articles/creating-releases/) you will still be able to attach a `.tar.gz` archive with a ready-to-use `configure` if you plan to publish new versions.