Add feature to programmatically update Changelog

Changelog (#17)

* Changelog file and parser

* Interface WIP

* Add changelog example usage

* ChangelogFile tests

* Update README

Added debug logs to the repository class, improved README example

Improved readme and added debug statements

* Improved readme and added debug statements

Bugfix

Fix repo files issue.
Fix an issue where multiple instantiations of Repo would utilize the same file array.

Create interface for manipulating objects in github files

• Create new interface for manipulating objects in files
• Update README with new interface
• Add comment explaining YAML representer
• Add test for BaseFile
• Make load/dump methods internal

Fix logging during dry-run

Merge pull request #3 from argoproj-labs/fix-logging

Only log when not dry run

Allow overriding Github API URL for Github Enterprise

Merge pull request #2 from argoproj-labs/override_github_url

Allow overriding Github URL for Github enterprise

Initial Release for Docker Hub Test

v0.1.5

Release to test DockerHub triggers

Initial Release for Docker

v0.1.4

Revving version to release images

Initial Git Release

v0.1.3

fixed secret ref