Update the tox configuration to use more modern python

tox.ini

@@ -1,28 +1,36 @@
 [tox]
-envlist = py27,py34,py35,py36,py36-pandas,py36-caching,py37,py38
+requires =
+  tox>=4
+env_list = py{27,34,35,36,36-pandas,36-caching37,38,39,310,311}
 
-[testenv]
-#changedir=tests
+[testenv:py36-pandas]
 deps=
   pytest
+  pandas
 commands=
-  #python tests/test.py
-  pytest -v tests/*.py
+  pytest -v {tox_root}/tests/gene.py::TestGeneClient::test_querymany_dataframe
+  pytest -v {tox_root}/tests/variant.py::TestVariantClient::test_querymany_dataframe
 
-[testenv:py36-pandas]
-#changedir=tests
+[testenv:py36-caching]
 deps=
   pytest
-  pandas
+  requests_cache
 commands=
-  pytest -v tests/gene.py::TestGeneClient::test_querymany_dataframe
-  pytest -v tests/variant.py::TestVariantClient::test_querymany_dataframe
+  pytest -v {tox_root}/tests/gene.py::TestGeneClient::test_caching
+  pytest -v {tox_root}/tests/variant.py::TestVariantClient::test_caching
 
-[testenv:py36-caching]
-#changedir=tests
+[testenv:py311]
+description = python3.11 pytest test suite execution
 deps=
+  pandas
   pytest
   requests_cache
 commands=
-  pytest -v tests/gene.py::TestGeneClient::test_caching
-  pytest -v tests/variant.py::TestVariantClient::test_caching
+  pytest -v \
+  "{tox_root}{/}tests{/}chem.py" \
+  "{tox_root}{/}tests{/}gene.py" \
+  "{tox_root}{/}tests{/}geneset.py" \
+  "{tox_root}{/}tests{/}test.py" \
+  "{tox_root}{/}tests{/}utils.py" \
+  "{tox_root}{/}tests{/}variant.py" \
+  {posargs}