update regex filter config name

Author: alexferl

Diff for: README.md

@@ -28,8 +28,8 @@ Jan  1 12:01:21 hostname appname[1234]: message
 ```
 Usage of ./tinysyslog:
       --address string                    IP and port to listen on. (default "127.0.0.1:5140")
-      --filter string                     Filter to filter logs with. Valid filters are: null and regex. Null doesn't do any filtering.
-      --filter-regex-filter string        Regex to filter with. No filtering by default.
+      --filter string                     Filter to filter logs with. Valid filters are: null and regex. Null doesn't do any filtering. (default "null")
+      --filter-regex string               Regex to filter with.
       --log-file string                   The log file to write to. 'stdout' means log to stdout and 'stderr' means log to stderr. (default "stdout")
       --log-format string                 The log format. Valid format values are: text, json. (default "text")
       --log-level string                  The granularity of log outputs. Valid level names are: debug, info, warning, error and critical. (default "info")

Diff for: config/config.go

@@ -73,7 +73,7 @@ func (cnf *Config) AddFlags(fs *pflag.FlagSet) {
 	fs.StringVar(&cnf.Address, "address", cnf.Address, "IP and port to listen on.")
 	fs.StringVar(&cnf.FilterType, "filter", cnf.FilterType, "Filter to filter logs with. Valid filters are: null and regex. " +
 		"Null doesn't do any filtering.")
-	fs.StringVar(&cnf.RegexFilter.Regex, "filter-regex-filter", cnf.RegexFilter.Regex, "Regex to filter with. No filtering by default.")
+	fs.StringVar(&cnf.RegexFilter.Regex, "filter-regex", cnf.RegexFilter.Regex, "Regex to filter with.")
 	fs.StringVar(&cnf.LogFile, "log-file", cnf.LogFile, "The log file to write to. "+
 		"'stdout' means log to stdout and 'stderr' means log to stderr.")
 	fs.StringVar(&cnf.LogFormat, "log-format", cnf.LogFormat, "The log format. Valid format values are: text, json.")