Update README.rst

Update box protocol link

Author: bigbes

README.rst

@@ -78,6 +78,6 @@ See More
 .. _`Tarantool Homepage`: http://tarantool.org
 .. _`Tarantool at Github`: https://github.com/tarantool/tarantool
 .. _`Tarantool User Guide`: http://tarantool.org/doc/user_guide.html
-.. _`Client-server protocol specification`: https://raw.github.com/tarantool/tarantool/master/doc/box-protocol.txt
+.. _`Client-server protocol specification`: http://tarantool.org/doc/dev_guide/box-protocol.html
 .. _`Sophia`: http://sphia.org
 .. _`BSD licensed`: http://www.gnu.org/licenses/license-list.html#ModifiedBSD