Update README.md

Author: cdujeu

README.md

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 This is the main source code repository of Pydio (formerly AjaXplorer), containing all the PHP server and HTML5 Web GUI.
 
-* Latest Stable release : 6.4.1
+* Latest Stable release : 6.4.2
 * Latest Dev release : 6.3.1 (was RC for Pydio 6.4)
 * License: [AGPLv3](https://www.gnu.org/licenses/agpl.html)
 * Lead developer  : Charles du Jeu (cdujeu): [Github](https://github.com/cdujeu) | [Twitter](https://twitter.com/Pydio)