document that hardlinks and symlinks are supported

it seems that hardlinks are supported, but were not explicitely documented in the documentation. the FAQ seems like the right place to do this. closes #133.

docs/faq.rst

@@ -17,6 +17,7 @@ Which file attributes are preserved?
 
     * Name
     * Contents
+    * Hardlinks and symlinks
     * Time of last modification (nanosecond precision with Python >= 3.3)
     * User ID of owner
     * Group ID of owner