- removed sources in the `library/` directory of the SimplePie lib as
those were for PSR-0 namespaces and we use PSR-4
- removed the PSR-4 autoloader provided by SimmpePie as we use our own
class loading mechanism
- updated the instructions in readme_moodle.txt
- fixed constants now being namespaced under \SimplePie\SimplePie
Signed-off-by: Daniel Ziegenberg <daniel@ziegenberg.at>