Fixed a volume mount issue when source and destination path differs

[jeremyVignelles]

Hi,
I had issues while mounting my containers volumes. After a quick investigation, I was able to fix the issue and publish this PR.

I also added tests for this, as well as the env option.

[jeremyVignelles]

I also noticed in README.md something saying:

  volumes: {
    '/root': '/tmp', // expose container /root to host /tmp
    '/root': '/tmp2:ro' // expose container /root to host /tmp2 as read only
  }

You can't have twice the same key in a JS object. Could you change the example to use two different directories there?

[jeremyVignelles]

Just added a fix for the same issue, but with port mappings, but didn't add a test as I have no idea how to test this. I can only confirm that it works with my container where the container's 80 port is mapped to host's 8080

[cmelion]

I tried this out and viewed the results in Kitematic. The folders were not linked properly.
The original repo adds extra entries, but it does allow proper navigation to host folders.