Release 0.5

[vtemian]

First major maintenance release.

In order to make the work as maintainable as possible, we'll drop support for old distributions and python 2.7. Besides that, we'll enforce black and other tools to increase the maintainability of the project.

We'll also need to update the builder for debs: https://github.com/presslabs/gitfs-builder

• update dependencies
• cleanup formatting problems with black
• add black as a CI requirement
• build a testing docker image
• add support for docker as a development tool (not intended for this release, it can be documented)
• fix tests
• manual test
  • fix merging error since we migrated to pygit 0.28.X
• support only ubuntu 18.04+
• update gitfs-builder for 18.04+
  • build libgit2 0.28.X for 18.04 +
• update brew formula (moved after release)