Update pull-request comment generation with threshold

[mikemimik]

Currently, the status in the PR comment just checks if (latest < current) then posts a result based on that. It's not very forgiving. Adding a threshold would be much better to reflect the vary in the results better.

[mikemimik]

There isn't a way to test this without the code being on master which is an issue. We should create a ticket to create a little testing around this to validate we don't break benchmarking.

[mikemimik]

closed with #4