fix: semver.diff prerelease to release recognition

[wraithgar]

Cleanup of #334
Closes#333

Authored by @deefactorial

[H4ad]

In this line:

node-semver/functions/diff.js

Lines 8 to 9 in b3a7d63

	constv1=parse(version1)
	constv2=parse(version2)

If we parse it first, we can speedup this from 300k op/s to ~470k to ~500k op/s.

Like this:

constv1=parse(version1)constv2=parse(version2)if(eq(v1,v2)){

Because eq also parse the version, so we parse it twice in this method without need.

Should I open another PR for this one?

EDIT: I opened a PR just to not mix the bugfix and the perf fix.

[nlf]

this one was a bit confusing and is a little unintuitive, but it does make sense. for future readers here's what helped me wrap my head around it:

the versions 1.0.0, 1.1.0-pre and 1.1.0 would sort in that same order. the transition from 1.0.0 to 1.1.0-precould be considered a pre-release, but it's also a minor and since the minor is the more impactful change that's what we report the diff as.