Update README.md

Adds release notes callout

README.md

@@ -5,6 +5,8 @@ Semantic is a set of specifications for sharing UI elements between developers.
 
 Semantic is production ready, but is formally "pre-release" until proper build and theming tools are available, and documentation is complete for all components.
 
+The project is under constant development, so be sure to check out our [release notes](https://github.com/jlukic/Semantic-UI/blob/master/RELEASE%20NOTES.md) for recent changes.
+
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 ### Bugs and Issues