add a changelog

Author: chris48s

CHANGELOG.md

@@ -0,0 +1,21 @@
+# Changelog
+
+## :package: [2.0.0](https://pypi.org/project/commitment/2.0.0/) - 2018-02-17
+
+### Backwards-incompatible changes
+* `GitHubCredentials` constructor signature changed from
+  * `__init__(self, repo, branch, name, email, api_key)` to
+  * `__init__(self, repo, name, email, api_key)`
+* `GitHubClient.push_file()` signature changed from
+  * `push_file(self, content, filename, message, encoding='utf-8')` to
+  * `push_file(self, content, filename, message, branch='master', encoding='utf-8')`
+
+### New Methods
+* `GitHubClient.create_branch()`
+* `GitHubClient.get_file_bytes()`
+* `GitHubClient.get_file_str()`
+* `GitHubClient.open_pull_request()`
+
+## :package: [1.0.0](https://pypi.org/project/commitment/1.0.0/) - 2017-10-29
+
+First Release