Don't invalidate cache on patch level increments

Change-Id: I4e23a5960a9280e68c723851db5d5d9bf2e658d6
diff --git a/R/KorAPConnection.R b/R/KorAPConnection.R
index a667f9a..9247af9 100644
--- a/R/KorAPConnection.R
+++ b/R/KorAPConnection.R
@@ -131,7 +131,13 @@
 }
 
 KorAPCacheSubDir <- function() {
-  paste0("RKorAPClient_", packageVersion("RKorAPClient"))
+  paste0("RKorAPClient_",
+         gsub(
+           "^([0-9]+\\.[0-9]+).*",
+           "\\1",
+           packageVersion("RKorAPClient"),
+           perl = TRUE
+         ))
 }
 
 setGeneric("apiCall", function(kco, ...)  standardGeneric("apiCall") )