tox: run tests against ZODB #183

until https://github.com/zopefoundation/ZODB/pull/183 gets merged, let's
run also the tests for this, since we have support for this extension.

tox.ini

 # zodbtools | tox setup
 [tox]
-envlist = py27-ZODB{3,4,5}, py3{6,7,8}-ZODB{4,5}
+envlist = py27-ZODB{3,4,5,devPR183}, py3{6,7,8}-ZODB{4,5,devPR183}
 
 [testenv]
 deps	=
@@ -26,5 +26,8 @@ deps	=
     ZODB5:  ZODB >=5.0,	<6.0dev
     ZODB5:  ZEO	 >=5.0, <6.0dev
 
+    # with the patches from https://github.com/zopefoundation/ZODB/pull/183
+    ZODBdevPR183: -e git+https://github.com/navytux/ZODB@7f5a67b3e0d2dcf2d13f18a42a82e526f6d4055c#egg=ZODB
+    ZODBdevPR183: ZEO >=5.0, <6.0dev
 
 commands= {envpython} -m pytest