Rearranged the practices and bug fixes

Just rearranged the practices to be located at the end of the document. I also added references to previous chapters before each practices.

Other minor bug fixes and spell chekings were performed.

![superman-logo-picture-myspace-layout-165499](https://f.cloud.github.com/assets/1539420/297812/b382965e-9547-11e2-8bab-e5fddd44ec29.jpg)