Accept "pos" as an alias for ctag and default certainty to 1 for TreeTagger

Fixes CoNLL-U-Treetagger compatibility.

Change-Id: I6301b3d826da8330ee33d83a286f765b08af04b6
diff --git a/t/script/archive.t b/t/script/archive.t
index 41389bb..b0244ca 100644
--- a/t/script/archive.t
+++ b/t/script/archive.t
@@ -103,15 +103,20 @@
   # That's not really stable on slow machines!
   my $out = stdout_from(sub { system($call); });
 
-  ok($out =~ m!\[\$(\d+?):1\/2\]!s, $call . ' pid 1');
+  ok($out =~ m!\[\$(\d+?):1\/3\]!s, $call . ' pid 1');
   my $pid1 = $1;
-  ok($out =~ m!\[\$(\d+?):2\/2\]!s, $call . ' pid 2');
+  ok($out =~ m!\[\$(\d+?):2\/3\]!s, $call . ' pid 2');
   my $pid2 = $1;
+  ok($out =~ m!\[\$(\d+?):3\/3\]!s, $call . ' pid 3');
+  my $pid3 = $1;
 
   isnt($pid1, $pid2, 'No PID match');
+  isnt($pid2, $pid3, 'No PID match');
+  isnt($pid1, $pid3, 'No PID match');
 
   ok($out =~ m!Processed .+?\/corpus-doc-0001\.json!s, $call);
   ok($out =~ m!Processed .+?\/corpus-doc-0002\.json!s, $call);
+  ok($out =~ m!Processed .+?\/corpus-doc-0003\.json!s, $call);
 
   ok(-d $output, 'Temporary directory still exists');
   my $json_1 = catfile($output, 'corpus-doc-0001.json');