feat: move to clap and update arguments

[filipstefansson]

What this PR is about:

I picked the previous argument parser (seahorse) becaue it was small and didn't have any dependecies, but it didn't work well when running under the cargo cli (cargo-semver major worked but not cargo semver major). This PR moves this project to clap, and with that I also made some changes to the API that was enabled by this switch:

- cargo semver major|minor|patch|pre
+ cargo semver bump major|minor|patch|pre

- cargo semver major --pre alpha
+ cargo semver bump major alpha

[filipstefansson]

Codecov Report

Merging #3 (8e7ffb9) into master (366fe6f) will increase coverage by 0.90%.
The diff coverage is 98.24%.

@@            Coverage Diff             @@
##           master       #3      +/-   ##
==========================================
+ Coverage   93.88%   94.79%   +0.90%     
==========================================
  Files           4        3       -1     
  Lines         229      192      -37     
==========================================
- Hits          215      182      -33     
+ Misses         14       10       -4     

Impacted Files	Coverage Δ
src/version.rs	90.90% <97.91%> (+5.90%)	⬆️
tests/integration.rs	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 366fe6f...8e7ffb9. Read the comment docs.