Composer fixes and updated the autoloading

PSR-0 is deprecated, and we should also be autoloading our tests in `autoload-dev`. We can easily move to PSR-4 without moving any of the files thus retaining bc for any people still requiring files manually. Let me know if you're fine with actually just moving the files up 2 levels in the interest of keeping things clean.
For consistency I'd use the escaped backslash `\\` at the end too