fix url since libgit2.github.com is not the correct domain

Author: schnow265

README.md

@@ -1,7 +1,7 @@
 luagit2
 =======
 
-LibGit2 bindings for Lua. [API Docs](http://libgit2.github.com/luagit2/)
+LibGit2 bindings for Lua. [API Docs](http://libgit2.github.io/luagit2/)
 
 libgit2 version
 ---------------