Change release version to v3.0.4

Author: zimmerle

CHANGES

@@ -1,5 +1,5 @@
-v3.0.4 - YYYY-MMM-DD (to be released)
--------------------------------------
+v3.0.4 - 2020-Jan-13
+--------------------
 
  - Fix: audit log data omitted when nolog,auditlog
    [@martinhsv]

headers/modsecurity/modsecurity.h

@@ -190,7 +190,7 @@ namespace modsecurity {
 
 #define MODSECURITY_MAJOR "3"
 #define MODSECURITY_MINOR "0"
-#define MODSECURITY_PATCHLEVEL "3"
+#define MODSECURITY_PATCHLEVEL "4"
 #define MODSECURITY_TAG ""
 #define MODSECURITY_TAG_NUM "100"