Binary search tree

[depial]

The runtests.jl include explicit testing of instantiation and searching (making up the first two test groups) which go beyond the tests in canonical-data.json.

I do have another testset which strictly follows canonical-data.json, and it can be used if instantiation and searching isn't explicitly tested (in fact, a non-mutable struct could be used), but I don't think that would be in the spirit of the exercise.

Other notes:

• The testest uses indentation to signify levels of the binary tree which are being tested.
• Difficulty is set at 8 due to use of mutable struct and tree traversal
• Field access methods have been supplied in the stub, but the struct definition is left to the student.

[ErikSchierboom]

@depial I'll let @cmcaine look at the Julia code. If this isn't reviewed in a week or so, please ping me.

[depial]

@ErikSchierboom there still hasn't been any further review. I think this is the exercise that is the most involved, as far as the code goes, so if you think it would be easier, I could try opening a PR with an exercise that has more straightforward code, and we could leave this one for later?

[ErikSchierboom]

I will look at this next week when I return to work!

[ErikSchierboom]

Thanks!

[depial]

Cheers!