More dashes for horizontal rule in design document

Author: kriskowal

design/README.md

@@ -6,7 +6,7 @@ intended to leave the reader at liberty to experiment with variations
 of this implementation that suit their own requirements, without missing
 any important details.
 
--
+---
 
 Suppose that you're writing a function that can't return a value immediately.
 The most obvious API is to forward the eventual value to a callback as an
@@ -1014,4 +1014,4 @@ It is a common pattern that remote objects have a fixed set of methods, all
 of which return promises.  For those cases, it is a common pattern to create
 a local object that proxies for the remote object by forwarding all of its
 method calls to the remote object using "post".  The construction of such
-proxies could be automated.  Lazy-Arrays are certainly one use-case.
+proxies could be automated.  Lazy-Arrays are certainly one use-case.