LIST(impl): Add map implementation

[SimonMeskens]

Can I get a code review to see if these are the kinds of PRs you want? I'm versed in rebase if you need changes to the commit structure too.

[axefrog]

Sorry for the slow reply (Sunday and whatnot). Going to review this now. On a side note, do you by any chance have Docker set up on your local machine? Travis is failing and nobody I know can seem to reproduce the error that Travis is reporting. See: https://travis-ci.org/frptools/collectable/jobs/259185345
Apparently if you run the Travis test instance in Docker, it'll reproduce the issue successfully. Unfortunately my machine seems to fail when installing prerequisites for Docker, so I haven't been able to figure the issue out yet, which means that pull requests always show up as build failures.

[axefrog]

Code's all good, and builds fine for me locally. Merged. Thanks!

[SimonMeskens]

Unfortunately, Docker doesn't want to install on my machine either and I haven't been able to find out why.

Thanks for the review, I'll move on to some more challenging PRs (wanted to make sure I understood the PR process first).

[axefrog]

Travis is finally building. Your future PRs should now actually reflect this.

[SimonMeskens]

Thanks, that's helpful