treat args with the same name (but in different subparsers) as different values

[vanyakosmos]

• [x] restructure Option class
• [x] add constructor attr
• [x] add simplified version of argument with help
• [x] some bug fixes
• [x] add docs and update readme

[codecov[bot]]

Codecov Report

Merging #12 into master will not change coverage. The diff coverage is 100%.

@@          Coverage Diff          @@
##           master    #12   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           7      8    +1     
  Lines         519    599   +80     
=====================================
+ Hits          519    599   +80

Impacted Files	Coverage Δ
argser/consts.py	100% <ø> (ø)	:arrow_up:
argser/fields.py	100% <100%> (ø)	:arrow_up:
argser/parse_func.py	100% <100%> (ø)	:arrow_up:
argser/logging.py	100% <100%> (ø)	:arrow_up:
argser/formatters.py	100% <100%> (ø)
argser/utils.py	100% <100%> (ø)	:arrow_up:
argser/parser.py	100% <100%> (ø)	:arrow_up:
argser/display.py	100% <100%> (ø)	:arrow_up:

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