[Tags] Support multiple tags files

We also apply --nth 1..2 by default to limit the search scope.

Close #106
Related #5, #329

bin/tags.pl

@@ -0,0 +1,15 @@
+#!/usr/bin/env perl
+
+use strict;
+
+foreach my $file (@ARGV) {
+  open my $lines, $file;
+  while (<$lines>) {
+    unless (/^\!/) {
+      s/^[^\t]*/sprintf("%-24s", $&)/e;
+      s/$/\t$file/;
+      print;
+    }
+  }
+  close $lines;
+}