update eth-tester to version that supports byzantium

Author: pipermerriam

setup.py

@@ -30,7 +30,7 @@
     setup_requires=['setuptools-markdown'],
     extras_require={
         'tester': [
-            "eth-tester[py-evm]==0.1.0-beta.22",
+            "eth-tester[py-evm]==0.1.0-beta.23",
             "py-geth>=2.0.1,<3.0.0",
         ],
         'testrpc': ["eth-testrpc>=1.3.3,<2.0.0"],