bump to 1.3.1. (#116)

Author: Kristjan Kosic

config.mainnet.json

@@ -1,12 +1,12 @@
 {
   "port": 4001,
   "address": "0.0.0.0",
-  "version": "1.3.0",
+  "version": "1.3.1",
   "fileLogLevel": "info",
   "logFileName": "logs/ark.log",
   "consoleLogLevel": "info",
   "trustProxy": false,
-  "minimumVersion": "1.3.0",
+  "minimumVersion": "1.3.1",
   "db": {
     "host": "localhost",
     "port": 5432,