Adds pre-commit config to run various lintersci_improvements

This ads black, isort, pyupgrade, and flake8 to pre-commit-config.yaml
There are also some small changes to travis.yml and tasks.py to reduce
some repeated configurations that should be consolidated into
setup.cfg. Most other changes are automated by the linter scripts.

1 files changed, 1 insertions, 0 deletions

diff --git a/examples/persistent_history.py b/examples/persistent_history.py
index bc62cb14..330e3537 100755
--- a/examples/persistent_history.py
+++ b/examples/persistent_history.py
@@ -10,6 +10,7 @@ import cmd2
 
 class Cmd2PersistentHistory(cmd2.Cmd):
     """Basic example of how to enable persistent readline history within your cmd2 app."""
+
     def __init__(self, hist_file):
         """Configure the app to load persistent history from a file (both readline and cmd2 history command affected).