Add PyInstaller build

[iyehuda]

Description

Add standard method for building with PyInstaller. Use staticx to generate a single static binary. PyInstaller and staticx builds given as Makefile targets pyinstaller and pyinstaller_static accordingly.

Contribution Guidelines

Please Read through the Contribution Guidelines.

Fixed Issues

Resolves #301

Contribution checklist

• [x] I have read the Contributing Guidelines.
• [x] The commits refer to an active issue in the repository.
• [ ] I have added automated testing to cover this case.

Notes

No functionality added, therefore, there's nothing to cover with tests.

[codecov-io]

Codecov Report

Merging #302 into master will increase coverage by 0.2%. The diff coverage is n/a.

@@            Coverage Diff            @@
##           master     #302     +/-   ##
=========================================
+ Coverage    59.8%   60.01%   +0.2%     
=========================================
  Files          39       39             
  Lines        1928     1928             
=========================================
+ Hits         1153     1157      +4     
+ Misses        775      771      -4

Impacted Files	Coverage Δ
kube_hunter/core/events/handler.py	90.9% <0%> (+1.01%)	:arrow_up:
kube_hunter/modules/discovery/ports.py	88.46% <0%> (+11.53%)	:arrow_up:

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[itaysk]

I'm unclear about the motivation for this pr, commented in the associated issue.