Sync with python_example

[dean0x7d]

As discussed in #4 and pybind/python_example#12, this syncs the example docs, defines version info and adds conda tests.

@SylvainCorlay main.cpp and docs/ are direct copies from python_example with a find and replace for python_example -> cmake_example. I hope that's fine.

[dean0x7d]

@wjakob I need your assistance to get AppVeyor running again for this repository. The webhooks for pushes and pull requests were lost when the repo was transferred to the pybind org. I recreated the AppVeyor project, but it doesn't install the webhooks since I don't have permission in the repo.

This can be solved in one of the following ways, but I believe you'll need to do it because of the permissions:

• Either create a new AppVeyor project.
• Or add the webhooks manually to point to my existing AppVeyor project.

The second one can be done by going into the setting of this repo, then wehooks, add a new one with the url pointing to the existing project. The 'pull request' and 'push' triggers need to be enabled.

Sorry for the trouble.
(There are no such issues on Travis.)

[wjakob]

I've made you an admin for the project -- can you change the webhook now?

[dean0x7d]

Cool, I didn't know that was an option.
I configured the webhooks. Everything is back up and running. Thanks!

[SylvainCorlay]

LGTM