Make INFO the default syslog severity level

Otherwise the severity is DEBUG.
diff --git a/heka/files/lua/decoders/generic_syslog.lua b/heka/files/lua/decoders/generic_syslog.lua
index 48e5262..1307e01 100644
--- a/heka/files/lua/decoders/generic_syslog.lua
+++ b/heka/files/lua/decoders/generic_syslog.lua
@@ -23,7 +23,7 @@
     Payload     = nil,
     Pid         = nil,
     Fields      = nil,
-    Severity    = nil,
+    Severity    = 6, -- INFO
 }
 
 local syslog_pattern = read_config("syslog_pattern") or error("syslog_pattern configuration must be specified")