BinWrapper basic implementation

[bprzybylski]

This pull request introduces the following functions:

• low_level_exec (low-level execution of any binary file),
• kbmag_bin_wrapper (middle-level execution of kbmag binaries),
• kbprog_call (high-level execution of the kbprog binary),
• wordreduce_call (hign-level execution of the wordreduce binary),

and the basic tests for the latter two functions. Note that the tests do not cover the following scenario:

• a directory with kbprog/wordreduce input files is non-default.

[codecov-io]

Codecov Report

Merging #3 into master will increase coverage by 24.87%. The diff coverage is 78.94%.

@@             Coverage Diff             @@
##           master       #3       +/-   ##
===========================================
+ Coverage   18.29%   43.16%   +24.87%     
===========================================
  Files           5        6        +1     
  Lines          82      139       +57     
===========================================
+ Hits           15       60       +45     
- Misses         67       79       +12

Impacted Files	Coverage Δ
src/KBmag.jl	100% <ø> (ø)	:arrow_up:
src/BinWrapper.jl	78.94% <78.94%> (ø)

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[kalmarek]

yay!