change "master" branch references to "main" (#104)

and incidentally remove a defunct Travis button from README.rst.

The default branch itself was changed long ago, but not the references
to it in code and documentation.

Author: rolandwalker

CHANGELOG

@@ -4,7 +4,8 @@
 
 (released on TBD)
 
-- Update license dates
+- Update license dates.
+- Change `master` branch references to `main`.
 
 ## Version 2.10.0
 

CONTRIBUTING.rst

@@ -39,14 +39,14 @@ Ready to contribute? Here's how to set up CLI Helpers for local development.
     $ pip install -r requirements-dev.txt
     $ pip install --editable .
 
-6. Create a branch for your bugfix or feature based off the ``master`` branch::
+6. Create a branch for your bugfix or feature based off the ``main`` branch::
 
-    $ git checkout -b <name-of-bugfix-or-feature> master
+    $ git checkout -b <name-of-bugfix-or-feature> main
 
 7. While you work on your bugfix or feature, be sure to pull the latest changes from ``upstream``.
    This ensures that your local codebase is up-to-date::
 
-    $ git pull upstream master
+    $ git pull upstream main
 
 8. When your work is ready for the CLI Helpers team to review it,
    make sure to add an entry to CHANGELOG file, and add your name to the AUTHORS file.

README.rst

@@ -2,13 +2,10 @@
 CLI Helpers
 ===========
 
-.. image:: https://travis-ci.org/dbcli/cli_helpers.svg?branch=master
-    :target: https://travis-ci.org/dbcli/cli_helpers
-
-.. image:: https://ci.appveyor.com/api/projects/status/37a1ri2nbcp237tr/branch/master?svg=true
+.. image:: https://ci.appveyor.com/api/projects/status/37a1ri2nbcp237tr/branch/main?svg=true
     :target: https://ci.appveyor.com/project/dbcli/cli-helpers
 
-.. image:: https://codecov.io/gh/dbcli/cli_helpers/branch/master/graph/badge.svg
+.. image:: https://codecov.io/gh/dbcli/cli_helpers/branch/main/graph/badge.svg
   :target: https://codecov.io/gh/dbcli/cli_helpers
 
 .. image:: https://img.shields.io/pypi/v/cli_helpers.svg?style=flat

release.py

@@ -74,7 +74,7 @@ def upload_distribution_files():
 
 
 def push_to_github():
-    run_step("git", "push", "origin", "master")
+    run_step("git", "push", "origin", "main")
 
 
 def push_tags_to_github():