Add to documentation on running with Docker

[cboyden]

As noted in issue #388 the documentation on running Wraith using Docker isn't sufficient for people unfamiliar with Docker run commands or Wraith. I couldn't find a public repo for that doc site. Here are some suggestions for updates to the instructions:

1. Install and configure Docker according to the instructions for your operating system.
2. Get the Wraith dockerfile: docker pull bbcnews/wraith
3. If you are starting fresh and don't already have Wraith configuration from a previous local setup, create a directory to hold configuration files and shots. For example, to store it all under your home directory (Unix or Mac):

cd
mkdir wraith
cd wraith
pwd

4. Create an alias to make it easy to run commands. You'll need the full output of the pwd command above to insert into the alias:
   alias docker-wraith="docker run -P -v /replace/with/output/from/pwd:/wraithy -w='/wraithy' bbcnews/wraith"
5. If you are starting fresh, run the setup command: docker-wraith setup
6. Now you can run standard Wraith commands: docker-wraith capture configs/capture.yaml

[jjok]

I don't think you need to do steps 2 and 5. They happen automatically when you first do docker run ....

[jjok]

Oh, never mind. I didn't have to do those steps because I manually created a config file.

[kyleskrinak]

I had to tweak this example to get this to work on Windows Docker CE. Note I've added the --rm flag to destroy the resulting image when done with the capture.

docker run --rm -P -v c:\path\to\wraith\dir:/wraithy -w=/wraithy bbcnews/wraith capture configs/capture.yaml

[Screenack]

One other thing: I was running a test against "127.0.0.1" which is inaccessible from the container. I used "host.docker.internal" instead, and wraith was able to access my local instance. Read here for more information.