added use_develop to tox, this basically runs a pip install -e .

tox.ini

@@ -1,12 +1,12 @@
 [tox]
 envlist = py39, style, coverage, check-manifest
-install_command=python -m pip install {opts} {packages}
+#install_command=python -m pip install {opts} {packages}
 
 # ENVS
 # ----------
 
 [testenv]
-wheel_pep517 = True
+usedevelop = True
 deps = 
 	-r {toxinidir}/requirements.txt
 	pytest
@@ -15,8 +15,8 @@ commands = pytest tests/ {posargs}
 [testenv:style]
 deps =
 	flake8
-	flake8-isort
 	flake8-black
+	flake8-import-order
 	fortran-linter
 skip_install = True
 commands =
@@ -32,6 +32,7 @@ skip_install = True
 commands = 
 	- coverage erase
 	pytest -v tests/ --cov pyforfluids/ --cov-fail-under 90 --cov-report term-missing
+	- coverage erase
 
 [testenv:check-manifest]
 skip_install = True