[FIX] Multiple parameters for route_v8

[maciej-wichowski]

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1. Improve encode_parameters method, so it processes dict parameters correctly. Here API expects multi-level dict to be expressed as key[sub1]=val1&key[sub2]=val2. The method supports only one level sub-dict, which as far as I know, should be enough.
2. Fix route_v8 - avoid, exclude and truck parameters were not fully supported.

Fixes #83

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 92.99%. Comparing base (a8f1b58) to head (e1e01ff). Report is 2 commits behind head on master.

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Additional details and impacted files

@@           Coverage Diff           @@
##           master      #84   +/-   ##
=======================================
  Coverage   92.98%   92.99%           
=======================================
  Files          26       26           
  Lines        1754     1755    +1     
=======================================
+ Hits         1631     1632    +1     
  Misses        123      123           

Flag	Coverage Δ
unittests	92.99% <100.00%> (+<0.01%)	:arrow_up:

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