Add more practice exercises

[YanniPapandreou]

Helps with task 'Add initial exercises' in #1.

This PR adds implementations for 8 more exercises:

1. nucleotide-count
2. allergies
3. leap
4. raindrops
5. protein-translation
6. grains
7. gigasecond
8. meetup

With these there are now 23 practice exercises.

[quintuple-mallard]

Looks good overall!

[IsaacG]

It's good practice to keep PRs small and targeted. A PR that changes the version should only change the version. Each additional exercise probably merits its own PR.

[YanniPapandreou]

It's good practice to keep PRs small and targeted. A PR that changes the version should only change the version. Each additional exercise probably merits its own PR.

I'm happy to close this and split this into several PRs - I just didn't want to create extra burden on @quintuple-mallard - and also wasn't sure who else is maintaining this track :) The commits are mostly atomic so wouldn't be too hard for me to go back and open several PRs

[IsaacG]

I'm happy to close this and split this into several PRs - I just didn't want to create extra burden on @quintuple-mallard - and also wasn't sure who else is maintaining this track :)

It's just the two of you maintaining this track for now.

Smaller PRs are also much easier to read and review!

[quintuple-mallard]

It's good practice to keep PRs small and targeted. A PR that changes the version should only change the version. Each additional exercise probably merits its own PR.

I'm happy to close this and split this into several PRs - I just didn't want to create extra burden on @quintuple-mallard - and also wasn't sure who else is maintaining this track :) The commits are mostly atomic so wouldn't be too hard for me to go back and open several PRs

In general I would prefer if you opened several smaller PRs instead of on large one, but in this case, it doesn't really matter.