Update README.md with information for prerelease branch

Author: Kristan Kenney

README.md

@@ -2,7 +2,7 @@
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 **Current stable release:** Version 1.0.1, released on June 25th, 2019.
 
-**Next planned release:** Version 1.0.2 - minor bug fixes & improvements, release date yet to be determined.
+**Next planned release:** Version 1.0.2 - minor bug fixes & improvements, currently available for testing in the **prerelease** branch. Please see "Installing development builds" for more information.
 
 What is Hestia Control Panel?
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