Change examples to make it easier to use

I was talking to a deviant and he attempted to use the example, since the included lib was removed the path wasn't changed to use the lib's file path. Also, He attempted to use this example on php 5.2.x.

Changes:
- Change examples to take into account that we are no longer including the PHP-OAuth2 library
- Add a check and error if php is not 5.3.0 or higher, Namespaces was not introduced until 5.3