Add clone URL, fix typos, add YouTube link.
Add clone URL, fix typos, add YouTube link.

langurmonkey/libgdx-contribs,PatrikMaier/libgdx-contribs,MonsterOfCookie/libgdx-contribs,manuelbua/libgdx-contribs,langurmonkey/libgdx-contribs,PatrikMaier/libgdx-contribs,klaus7/libgdx-contribs,klaus7/libgdx-contribs,manuelbua/libgdx-contribs,MonsterOfCookie/libgdx-contribs