Add a CHANGELOG file

[saily]

To make it easier for people upgrading to bleeding edge version of your great django-webpack-loader it makes sense to check CHANGELOG first, before upgrading.

[shapiromatron]

I can take a shot at an initial PR if you'd like; I can pull the content out of the tags and scrape the changes for v.0.4 and v.0.5 if you'd like; let me know if that's something you want @owais

[saily]

@shapiromatron there are some tools which can create CHANGELOG files out of commit history but starting with a simple CHANGELOG.md file - in which every new feature/bugfix/change must be mentioned - would already help people upgrading.

[owais]

Sound great @shapiromatron @saily. A PR would be great. Let's start with something simpler like @saily said.

[owais]

Thanks @shapiromatron