Docker-based CI
Created by: bochecha
Note: Just like for libcangjie, I couldn't just push to @yookoala's branch since it is in his fork. As such I had to open a new pull request.
This is based off of @yookoala's work in #99
I rebased it on the latest master, cleaned it up a bit, and made some modifications:
- I removed the local testing, as there's really no point
- I parametrized the FROM line in the same way I had done for libcangjie
- I made it use the pre-built libcangjie images, instead of building them before building pycangjie