Added the Apache License, Version 2.0

On your [Code Project](http://www.codeproject.com/Articles/20823/Barcode-Image-Generation-Library) article, it mentions that the source is licensed under the [Apache License, Version 2.0](http://opensource.org/licenses/apache2.0.php). The license needs to be added to this repository to be licensed correctly ([read more here for the reason why](http://www.infoworld.com/article/2611422/open-source-software/github-finally-takes-open-source-licenses-seriously.html).)