Add option -Z to exclude empty texts

Change-Id: I1f2594ce839351205ce43b5047b349af7ba019bb
diff --git a/src/test/resources/simple.conllu b/src/test/resources/simple.conllu
index 5a907cc..48dc9fc 100644
--- a/src/test/resources/simple.conllu
+++ b/src/test/resources/simple.conllu
@@ -1,5 +1,5 @@
 # text_id = TST_TST.00001
-# empty texts are expected to count
+# empty texts are expected to count *not*
 
 # text_id = TST_TST.00002
 1	ich	ich	PPER	PPER	_	_	_	_	1
@@ -26,6 +26,6 @@
 # make sure that an empty text header does no harm
 
 # text_id = TST_TST.00007
-# in the unigrams we should have 7 start and end tags
+# in the unigrams we should have 3 start and end tags, because empty texts do not count starting with v2.2.3