Add list of publicly available signalhubs (#29)

README.md

@@ -85,6 +85,14 @@ signalhub subscribe my-app my-channel -p 8080 -h yourhub.com
 
 This also works in the browser using browserify :)
 
+## Publicly available signalhubs
+
+Through the magic of free hosting, here are some free open signalhub servers!
+For serious applications though, consider deploying your own instances.
+
+- https://signalhub-jccqtwhdwc.now.sh
+- https://signalhub-hzbibrznqa.now.sh
+
 ## Deploying with popular services
 
 No additional configuration is needed.