Test hamcrest with Docker

Simple testing steps

(this assumes that you have Docker installed)

1. cd to the directory containing PyHamcrest's tox.ini file.
2. run docker run --rm -v $(pwd):/src chrisr/pybuilder:latest

That's it!

This will test PyHamcrest with all supported versions of Python

Tweaking the build image

1. in this directory, modify the Dockerfile to have the setup you want
2. docker build --tag $USER/pybuilder:latest .
3. run your build
4. submit a pull request to the hamcrest/PyHamcrest repo with your changes to the Dockerfile

We'll merge and publish the new tag to chrisr/pybuilder:latest, making the new instructions up to date.