Fix failing tests due to precision errors on arm64

[Gu1nness]

Co-authored-by: @nbraud
Fixes #33

[nicoonoclaste]

FYI, this can be tested without access to a non-amd64 machine, using qemu-user-static.
Just GOARCH=arm64 go test will work, thanks to some binfmt magic.

[coveralls]

Coverage remained the same at 100.0% when pulling 2c61242 on Gu1nness:fix-tests-outside-amd64 into ed2e831 on montanaflynn:master.

[anthonyfok]

Thank you so much @Gu1nness and @nbraud! This is an awesome fix to #33!

There is only one tiny thing I would recommend, and that is to run go fmt and push to this pull request again, and that would unify the spacing for correlation_test.go, test_utils_test.go, util.go.

Many thanks!

[nicoonoclaste]

@anthonyfok I was hoping you'd have a suggestion for a better place to put test utilities than test_utils_test ;3

[anthonyfok]

@nbraud Ha ha! I didn't look too closely at the rest of the patch / pull request yet, but in my limited (and abandoned) experiment, I named it tolerance_test.go so it matches the main function tolerance() therein, but with the disadvantage that it looks too much like one of the other features (e.g. variance.go and variance_test.go), so your naming of test_utils_test.go is good that it is unambiguous. ^_^

[montanaflynn]

This fails for older Go versions which won't accept an argument in an en Example test:

https://travis-ci.org/github/montanaflynn/stats/builds/749863684

[montanaflynn]

I think we could use stats.Round here with the same result and added benefit of showing off another exported function instead of a private function that cannot be copy / pasted as one would expect from an example.

[montanaflynn]

Great work @Gu1nness and @nbraud, happy to see this solved!

I see it failed tests for older Go versions: https://travis-ci.org/github/montanaflynn/stats/builds/749863684 and left some comments on how I think we could fix that and improve the example at the same time.

I also agree with @anthonyfok that running go fmt to fix the spacing so it matches and doesn't result in the next PR having unrelated formatting changes would be good.

Once the formatting and example changes are pushed I'll be glad to merge!

[montanaflynn]

I made the changes and added tests for arm64 on travisci, and they all passed! 🎉

I've also merged the PR into master, they will be included in a new tagged release soon.