To support websockify's BaseTokenAPI token plugin: https://git.io/fjpXb.
Resolves:
```
WebSocket server settings:
- Listen on :80
- No SSL/TLS support (no cert file)
- proxying from :80 to targets generated by BaseTokenAPI
172.17.0.1 - - [02/Sep/2019 16:55:46] code 405, message Method Not
Allowed
handler exception: No module named requests
```
As websockify has been updated over the years, there is no longer:
- `LICENSE.txt` (removed in 368ec2c)
- `*.html` (removed in 368ec2c)
I have also opted to remove `README.md` as I do not believe it is
necessary to be inside the container.
Since the time of authoring this PR, Alpine has since gained numpy
support. This commit updates the Dockerfile to use mainline Alpine and
use `apk`'s py-numpy package.
Brooks Swinnerton