Added --version option in the same manner as --help.

[pcoltau]

I've added a --version option in the same manner as the --help option.

The version can be provided in the ArgParser constructor if needed. If it is not provided, no --version option will be added. This makes the change fully compatible with older versions of the ArgParser.

I've also added a -v option for the version, but I'm unsure if this is wanted. Let me know, and I can remove it.

[codecov-io]

Codecov Report

Merging #70 into master will increase coverage by 0.31%. The diff coverage is 100%.

@@             Coverage Diff              @@
##             master      #70      +/-   ##
============================================
+ Coverage      84.9%   85.21%   +0.31%     
- Complexity      138      139       +1     
============================================
  Files            11       11              
  Lines           424      433       +9     
  Branches         84       85       +1     
============================================
+ Hits            360      369       +9     
  Misses           27       27              
  Partials         37       37

Impacted Files	Coverage Δ	Complexity Δ
...main/kotlin/com/xenomachina/argparser/ArgParser.kt	91.12% <100%> (+0.25%)	55 <0> (+1)	:arrow_up:
...ain/kotlin/com/xenomachina/argparser/Exceptions.kt	95.65% <100%> (+0.65%)	0 <0> (ø)	:arrow_down:

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[pcoltau]

Any chance of getting this merged?

[Malinskiy]

+1 for this change