Demo project for building Python+PyPy wheels for Linux with Travis-CI

This is a fork of the official python-manylinux-demo project. Building PyPy wheels is as easy as changing the docker image to use, as shown by this commit.

diff --git a/.travis.yml b/.travis.yml
index 51e4a73..990950e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,7 +17,7 @@ matrix:
     - sudo: required
       services:
         - docker
-      env: DOCKER_IMAGE=quay.io/pypa/manylinux2010_x86_64
+      env: DOCKER_IMAGE=pypywheels/manylinux2010-pypy_x86_64
            PLAT=manylinux2010_x86_64

This works because the default script builds a wheel for every python installation found in /opt/python, which now includes also PyPy.

If your build system is more elaborate or you want to build wheels for only selected versions of CPython/PyPy, you probably need to tweak your scripts and build wheels using e.g. /opt/python/pp271-pypy_41/bin/python.