Add processing pipelines

[codders]

In preparation for a more diverse feature-set, I've refactored the code so that exposes are passed through a number of filtering / transformation steps. These steps can be joined into a pipeline, which is applied to the results of a crawl to give the processed exposes.

[codecov-commenter]

Codecov Report

Merging #11 into master will increase coverage by 4.92%.
The diff coverage is 91.30%.

@@            Coverage Diff             @@
##           master      #11      +/-   ##
==========================================
+ Coverage   70.40%   75.32%   +4.92%     
==========================================
  Files          12       16       +4     
  Lines         669      758      +89     
  Branches       81       92      +11     
==========================================
+ Hits          471      571     +100     
+ Misses        172      155      -17     
- Partials       26       32       +6     

Impacted Files	Coverage Δ
flathunter/gmaps_duration_processor.py	76.36% <76.36%> (ø)
flathunter/hunter.py	81.39% <88.88%> (+32.37%)	⬆️
flathunter/default_processors.py	92.85% <92.85%> (ø)
flathunter/abstract_processor.py	100.00% <100.00%> (ø)
flathunter/config.py	66.03% <100.00%> (-33.97%)	⬇️
flathunter/filter.py	85.12% <100.00%> (+0.91%)	⬆️
flathunter/processor.py	100.00% <100.00%> (ø)
flathunter/sender_telegram.py	89.65% <100.00%> (+2.15%)	⬆️
... and 3 more

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