Update README.md

Author: fussegli

README.md

@@ -1,6 +1,6 @@
 # MATBOX: Microstructure Analysis Toolbox
 **MATLAB open source microstructure analysis code embedded with a graphic user interface**\
-*v1.0 May 18, 2021*\
+*v1.0a May 19, 2021*\
 See release_notes.txt for a change log.
 
 ![MATBOX](https://github.com/NREL/MATBOX_Microstructure_analysis_toolbox/blob/master/MATBOX_logo.png)