implemented Index.AddAll, Index.RemoveAll, Index.UpdateAll
Remove Config#Refresh

Because it has been removed from libgit2:
https://github.com/libgit2/libgit2/commit/55cb4999720f46eddb97e25e7ddc6ac068dd0bae
Update libgit2 submodule.
Merge pull request #128 from calavera/remote_git_config_refresh_call

Remove Config#Refresh
Merge pull request #125 from lucas-clemente/master

implemented Index.AddAll as git_index_add_all wrapper
Merge branch 'master' into ls_remote

* master:
  Update libgit2 submodule.
  Remove Config#Refresh
  implemented Index.AddAll, Index.RemoveAll, Index.UpdateAll
Add connect methods to Remote.
Make filtering logic more simple.