Added version command

[volaya]

fixes #123

[codecov-commenter]

Codecov Report

Merging #127 (4f3ba13) into master (7e67bce) will increase coverage by 0.14%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #127      +/-   ##
==========================================
+ Coverage   85.26%   85.40%   +0.14%     
==========================================
  Files          82       83       +1     
  Lines        2463     2473      +10     
==========================================
+ Hits         2100     2112      +12     
+ Misses        363      361       -2     

Impacted Files	Coverage Δ
stactools_cli/stactools/cli/__init__.py	100.00% <100.00%> (ø)
stactools_cli/stactools/cli/commands/version.py	100.00% <100.00%> (ø)
stactools_core/stactools/core/version.py	100.00% <0.00%> (+100.00%)	⬆️

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