Moving to namespace Emojione

This is step 1 for #24.

Emojione is now in ```Emojione\Emojione``` and can be autoloaded via [PSR-4](http://www.php-fig.org/psr/psr-4/). I also moved the class to ```lib/php/src``` so we can create eg ```lib/php/tests``` in future for tests. I hope it will not to difficult to update the DB generating tool.

I've also updated the demos but I'm not sure if I found all declarations of Emojione. Please take a look if i forgot something.

Because of splitting the class in future we would have multible files and have to require all files in demos first. To avoid this work in future I wrote a simple autoloader in ```lib/php/autoload.php``` which we can easily update.