added release date

changelog.md

 Changes in tpcclib
 ==================
 
-## version 0.6.17 (under development)
+## version 0.6.17 (2017-12-31)
 
 - Imported application pdoc2htm.
 - Imported and rewritten application fit_gvar.
@@ -32,7 +32,7 @@ Changes in tpcclib
 - Fixed bug in parSelectTACs() and parSelectParameters() in v2.
 - Changed to prevent truncation warnings regarding sprintf in Ubuntu gcc 7.2.0.
 
-## version 0.6.16
+## version 0.6.16 (2017-09-26)
 
 - Added applications imgfrdif, imgmaxp, maskconj, maskinv, and mask2pxl in v1.
 - Added application iftvalc in v2.