added tag-triggered test

ensure tag and libzstd version are compatible

.travis.yml

@@ -26,6 +26,10 @@ matrix:
 
     - env: Cmd='make lz4install && make -C tests test-lz4'
 
+    # tag-specific test
+    - if: tag =~ ^v[0-9]\.[0-9]
+      env: Cmd='make -C tests checkTag && tests/checkTag $TRAVIS_BRANCH'
+
 git:
   depth: 1