Added command to output version

[ansasaki]

Avoid repetition when writing to file.

Added command to get the current version.

Also added version to output. This required changes in the tests expected output files.

Added a way to easily update the version in tests.

Updated readme and usage documentation.

Added script to get the current version to be used in bootstrap.

[coveralls]

Pull Request Test Coverage Report for Build 111

• 31 of 31 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 97.857%

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Totals
Change from base Build 107:	0.1%
Covered Lines:	730
Relevant Lines:	736

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💛 - Coveralls

[codecov-io]

Codecov Report

Merging #66 into master will increase coverage by 0.19%. The diff coverage is 100%.

@@            Coverage Diff            @@
##           master     #66      +/-   ##
=========================================
+ Coverage    96.4%   96.6%   +0.19%     
=========================================
  Files           3       4       +1     
  Lines         723     736      +13     
  Branches      187     189       +2     
=========================================
+ Hits          697     711      +14     
  Misses          6       6              
+ Partials       20      19       -1

Impacted Files	Coverage Δ
src/smap/symver.py	96.54% <100%> (+0.2%)	:arrow_up:
src/smap/__init__.py	100% <100%> (ø)	:arrow_up:
src/smap/_version.py	100% <100%> (ø)

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