[cmake] Add playTests.sh as a test

.travis.yml

@@ -84,7 +84,7 @@ matrix:
         - make clean
         - make -j check MOREFLAGS="-Werror -DZSTD_NO_INLINE -DZSTD_STRIP_ERROR_STRINGS"
 
-    - name: cmake build check    # ~2mn
+    - name: cmake build and test check    # ~2mn
       script:
         - make cmakebuild