ch7 add tests and solutions

[milesfrain]

No description provided.

[oldfartdeveloper]

I'd like to do this one.

[milesfrain]

Heads-up that #127 also touched parts of ch7. I don't think it will directly affect the work you're doing, but it may be wise to rebase sooner than later to avoid merge conflicts.

git pull --rebase upstream master

Assuming git remote -v shows something like this:

git remote -v
upstream        https://github.com/purescript-contrib/purescript-book.git (fetch)
upstream        https://github.com/purescript-contrib/purescript-book.git (push)

You can add an upstream with:

git remote add upstream https://github.com/purescript-contrib/purescript-book.git

[oldfartdeveloper]

@milesfrain Thanks; I've been rebasing and, indeed, have had the identical remote upstream defined. I'm almost certain that #127 will affect the upcoming exercises, so I merged it; thanks for the heads-up.

[oldfartdeveloper]

@milesfrain I'm replacing PR #126 with this new one #146. #126 swept too many files into it; just easier to close that one and submit this one.