Link to doc files

GitHub markdown supports linking to relative files.

README.md

@@ -46,9 +46,10 @@ or available to root and you may want to maintain different configuration for
 `ssh` on your personal and your work machines.
 
 A lot of modern UNIX-based systems offer packages for `vcsh`. In case yours
-does not read `INSTALL.md` for install instructions or `PACKAGING.md` to create
-a package, yourself. If you do end up packaging `vcsh` please let us know so we
-can give you your own packaging branch in the upstream repository.
+does not read [`INSTALL.md`](doc/INSTALL.md) for install instructions or
+[PACKAGING.md](doc/PACKAGING.md) to create a package, yourself. If you do end
+up packaging `vcsh` please let us know so we can give you your own packaging
+branch in the upstream repository.
 
 ## Talks