create EELS TransitionTool subclass

Author: gurukamath

conftest.py

@@ -0,0 +1,8 @@
+import pytest
+from ethereum_spec_tools.evm_tools.t8n.transition_tool import EELST8N
+from ethereum_clis import TransitionTool
+
+
+@pytest.hookimpl(tryfirst=True)
+def pytest_configure(config):
+    TransitionTool.set_default_tool(EELST8N)