Assignment bugfix

[CasBex]

I implemented an in-place and out-of-place version of one of the simple sorting algorithms.

There's the following bugs/problems that I can spot right out-of-the-box

1. mysort doesn't pass reverse to mysort!
2. A reverse sort for AbstractArray{T} could fail due to the non-existence of (-)(::T) (e.g. arrays of strings)
3. A reverse in-place sort is not actually mutating and has a return value
4. While mysort is type-stable, the return type can be weird. For example mysort(::String) -> Vector{Char}
5. mysort! will fail for arrays with weird indices (e.g. OffsetArrays)

Steps for completing this assignment are as follows:

• Mentee files an issue with FixMe.jl
• Mentee fixes these problems
• Mentee writes some tests and uses these to show that their fix is working
• Mentee makes a PR to FixMe.jl
• Mentor does code review, prompts the mentee to make some tests and asks guiding questions when the mentee doesn't spot some of the above problems.
• Mentor merges PR to his fork

Before merging we should at least take this for a test drive. I'm looking for volunteer mentors/mentees.
If it's approved after the test-drive (or after some iteration) the README should be updated with instructions.

• Test drive the assignment
• Add to README