Add URL-based install to Readme

Readme.md

@@ -6,7 +6,11 @@ Convert a DOM [DocumentType](https://developer.mozilla.org/en-US/docs/Web/API/Do
 
 ## Install
 
-    npm install doctype-to-string
+    npm install "git+https://code.treora.com/gerben/doctype-to-string#latest"
+
+    npm install doctype-to-string@latest
+
+..or equivalent
 
 ## Usage