fix: FrameTimeCode approximation flooring instead of rounding

[Wirg]

Suggested solution to #268 .

[Breakthrough]

As discussed in #268, please re-target this change for the v0.6 branch, and update the failing unit tests so that the build passes. Thanks for your help!

[Breakthrough]

Also I think there are some edge cases your change might not have covered where there is still truncation happening - I'd be happy to fix that up if you aren't able to.

It's probably better to just use _seconds_to_frames everywhere there's an int(...) expression.

Thanks!

[Breakthrough]

Sorry for the comment spam - I've merged your fix into v0.6 as per c5ac42b.

Unfortunately I'll need to close this PR as it constitutes a breaking change for v0.5 which may cause unintended side effects. However, this will definitely be fixed for v0.6 and will be included in the next/final beta release.

Thanks so much for the PR and suggested solution.