Document that hard links work

[wscott]

After reading the FAQ that lists the set of metadata saved and not seeing information for hard links, I just wrote up a whole description about how hard links could be supported.
Then I did some testing and found that it works correctly.

You might want to update the FAQ to list that hardlinked files are saved and restored correctly.

[anarcat]

i think this should be closed in favor of the #155 PR.