update version and CHANGES

CHANGES

+26/10/2019 V2.1.3
+
+Improved the zone radius calculator in DISCS.
+
+Fixed a bug in the macro to detect true/false as a command line argument.
+
+Rewritten individual_novae to use the events framework, and removed its
+dodgy pre-event code that was supposed to do the same thing (kind of).
+
 02/10/2019 V2.1.2
 
     add new "overspin_algorithm" option to handle what happens

src/binary_c_version.h

@@ -30,7 +30,7 @@
  * 
  * Patch is zero for a major release.  
  */
-#define BINARY_C_VERSION "2.1.2"
+#define BINARY_C_VERSION "2.1.3"
 
 /* and a CEMP run version */
 #define CEMP_VERSION "prelim10-O1-noCNEMPs"