Add isort, black and flake8 to dev-requirements.txt (+ remove support to pylint).

.pylintrc

@@ -1,25 +0,0 @@
-[MAIN]
-py-version=3.8.0
-
-[MESSAGES CONTROL]
-disable=
-    missing-docstring,
-    multiple-imports,
-    too-few-public-methods,
-    too-many-instance-attributes
-
-[VARIABLES]
-allowed-redefined-builtins=all,dir,format,id,len,type
-
-[FORMAT]
-max-line-length=120
-expected-line-ending-format=LF
-
-[BASIC]
-good-names=f,t,id,ip,on,pl,tf,to,A,B,C,D,E,F
-
-[TYPECHECK]
-generated-members=websockets
-
-[STRING]
-check-quote-consistency=yes