🚀 go-pugleaf

This is really several changes which are independent:

* Store the lock file in the same dir as the visited file.
* Store user name and host name in the lock file.
* Use a symlink.

Here's what I think of them:

* Store the lock file in the same dir as the visited file.

This fails if you can write the file but you cannot write its
containing directory.  It also fails on systems with short file names.
I don't see any particular advantage in it.  So I am not making this
change.

* Store user name and host name in the lock file.

This can't hurt; it will help if someone implements the demon, but
until then it does not help.  I think I might as well put this
info into the file.

* Use a symlink.

This can't hurt, but it is just a minor improvement.