Version parsing v2

[r2d4]

just to test out https://github.com/GoogleContainerTools/skaffold/pull/1020/files#r220053214

1. about 50% less code
2. more functionality (from blang/semver)
3. 100% test coverage apiversion.go + relying on a tested version library (blang/semver) vs. a custom one

[googlebot]

So there's good news and bad news.

👍 The good news is that everyone that needs to sign a CLA (the pull request submitter and all commit authors) have done so. Everything is all good there.

😕 The bad news is that it appears that one or more commits were authored or co-authored by someone other than the pull request submitter. We need to confirm that all authors are ok with their commits being contributed to this project. Please have them confirm that here in the pull request.

Note to project maintainer: This is a terminal state, meaning the cla/google commit status will not change from this state. It's up to you to confirm consent of all the commit author(s), set the cla label to yes (if enabled on your project), and then merge this pull request when appropriate.

[codecov-io]

Codecov Report

Merging #1026 into master will increase coverage by 0.31%.
The diff coverage is 88.88%.

@@            Coverage Diff             @@
##           master    #1026      +/-   ##
==========================================
+ Coverage   40.86%   41.17%   +0.31%     
==========================================
  Files          70       72       +2     
  Lines        3091     3121      +30     
==========================================
+ Hits         1263     1285      +22     
- Misses       1703     1707       +4     
- Partials      125      129       +4

Impacted Files	Coverage Δ
pkg/skaffold/config/config.go	0% <ø> (ø)	⬆️
pkg/skaffold/apiversion/apiversion.go	100% <100%> (ø)
cmd/skaffold/app/cmd/util/util.go	55.55% <66.66%> (ø)

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[dgageot]

@r2d4 this needs to be rebased

[googlebot]

CLAs look good, thanks!

[r2d4]

done 👍