Better error message when track/problem can't be identified

[anxiousmodernman]

I've created two error messages for two scenarios.

1. If submit is called outside of the configured exercises directory, use the msgSubmitCalledFromWrongDir template
2. If submit is called inside the configured exercises directory, but the path seems weird, use msgGenericPathError template. I was able to simulate this error like this:

cd ~/exercism   # my exercism home
mkdir tmp
cd tmp
touch Clock.go
exercism submit Clock.go

Happy to rework any of this. 🎅 🎄 🎁

I used text/template because the messages were quite long. The iterationError type is not necessary, strictly speaking, but I'd like to know what the rest of the team thinks.

It was mentioned in #197 that we could suggest the proper path. I am unsure how to do that without having some kind of lookup based on file extension and the exercise slug. Even if I know that the file they're trying to submit is JavaScript, how can I tell it's the hello-world problem when they're submitting from a bad path/location?

[kytrinyx]

s/helloworld/hello-world

[kytrinyx]

This looks great! I really like the clarity of these error messages, and I think using a text/template was a really good call. I have a few minor comments.

[anxiousmodernman]

I think this is done. Please review when you are able.

[kytrinyx]

Thanks so much for taking the time to work through this so thoroughly!