Add fuzz tests on Float to Quantity and Quantity to Float functions

[mdevlamynck]

Fixes #5.

Adds a function to fuzz test conversion from Float to Quantity and Quantity to Float and use it to test all such conversion functions.

While doing this I noticed that Pixels.pixelsPerSecondSquared and Pixels.inPixelsPerSecondSquared are not exposed. Is this on purpose or a mistake?

[ianmackenzie]

Thanks for the PR, looks good! Just a couple comments (these are entirely my fault for not having set up a proper CONTRIBUTING.md yet):

• I've just added an AUTHORS file; can you add yourself to it? You don't have to include your e-mail address if you'd prefer not to, but something like a GitHub username or other way to contact you would be great.
• For any future PRs, it's slightly cleaner to make changes in a branch of your fork, make a PR from that branch, and then delete the branch when the PR is merged (or otherwise closed). This keeps your master branch as a perfect copy of the upstream repository, which is important especially if the PR is not merged (since then the commits you added in your master branch will never show up in the upstream master and the two will become out of sync). (It also means you can more easily have multiple PRs open at the same time and work on them in parallel.)

By the way, am I correct in assuming you found this through Hacktoberfest? It's always nice to know that it is indeed worth the little bit of time effort to find and prepare Hacktoberfest-friendly issues =)

[mdevlamynck]

• No problems, I'll add myself in the AUTHORS files.
• Yes I usually create a separate branch, don't know why I didn't think doing it this time ^^ Do you want me to create one?
• Indeed I found this repo through Hacktoberfest. I really love the concept.

[ianmackenzie]

No, don't worry about the branch, that's really more for your benefit...and this pull request will get merged very soon, so you shouldn't have to worry about your fork getting out of sync =)

Oh, and I forgot to mention but yes the pixelsPerSecondSquared/inPixelsPerSecondSquared was just a plain oversight on my part - thanks for catching that!