Update libgit2 to 3f8d005

Updating libgit2 to `0a62918`.  The current version in HEAD (`0383fa`) had an unfortunate bug updating the tree cache (https://github.com/libgit2/libgit2/issues/2629) that can cause some issues.
Sure - I changed the text ever so slightly (to lead with the nonexistent
ref), but let me know if you prefer your text.

On Mon, Nov 3, 2014 at 6:35 PM, nulltoken <notifications@github.com> wrote:

> In LibGit2Sharp/Core/Proxy.cs:
>
> >                      {
> > -                        int res = NativeMethods.git_remote_rename(
> > -                            ref array.Array,
> > -                            remote,
> > -                            new_name);
> > +                        throw new NotFoundException("The given remote was not found");
>
> How about string.Format("Remote '{0}' hasn't been renamed as it doesn't
> exist.", name)?
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/libgit2/libgit2sharp/pull/857/files#r19775923>.
>