set the version of the snap using git tags

[come-maiz]

closes #1436

[come-maiz]

This is a new feature in the latest released snapcraft. If the snap being build is from a revision with a git tag, it will use that tag as the version. If it's not a tag, it will use still form a readable version using the latest git commit.

I also have some more good news. We have https://build.snapcraft.io/ in beta. In there you can configure your continuous delivery, so it will take care of building the snaps for you and publishing them to the store. Please give it a try and let me know how it works.

[codecov-io]

Codecov Report

Merging #1491 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1491   +/-   ##
=======================================
  Coverage   98.38%   98.38%           
=======================================
  Files          56       56           
  Lines        2597     2597           
=======================================
  Hits         2555     2555           
  Misses         42       42

[sbellem]

Thanks @ElOpio !

[krish7919]

Thanks, @ElOpio .