fixed bug that produced wrong overhang in linear, non-directional, single cut reactions.

Changes in this PR

fixed bug that produced wrong overhangs in linear, non-directional, single cut reactions.

Why are you making these changes?

There was a bug in CutWithEnzyme where in the case of linear, non-directional, single cut reactions, it would assume that the overhangs were produced by a forward facing cut site and return a sequence downstream. In the case of the cut being a reverse cut site it would return the wrong overhangs. This was fixed with a simple if-else

Are any changes breaking? (IMPORTANT)

There are no breaking changes.

Pre-merge checklist

All of these must be satisfied before this PR is considered ready for merging. Mergeable PRs will be prioritized for review.

[x] New/changed functionality is thoroughly tested.
[x] New/changed functionality has a function giving an example of its usage in the associated test file. See primers/primers_test.go for what this might look like.
[x] Changes are documented in CHANGELOG.md in the [Unreleased] section.
[x] All code is properly formatted and linted.
[x] The PR template is filled out.

bebop / poly