Fix deploy instructions in the README

Signed-off-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
diff --git a/README.md b/README.md
index 19e8b29..6abfd6c 100644
--- a/README.md
+++ b/README.md
@@ -12,7 +12,9 @@
 properties can be used to specify their respective deploy locations.
 For example:
 
-    mvn clean deploy -Dmaven-deploy-destination=/var/www/traces/maven -Dp2-deploy-destination=/var/www/traces/repository
+    mvn clean deploy -Dmaven-deploy-destination=file:///var/www/traces/maven -Dp2-deploy-destination=/var/www/traces/repository
+
+(Note that the first property needs a `file:///` scheme, but the second does not.) 
 
 You can then point depending projects to these locations.