add Bpost and PostNL support

[kenny-inventis]

Add support for Bpost and PostNL.

[loevgaard]

Can you rebase onto master :)

[codecov]

Codecov Report

Merging #63 (f3a6712) into master (eeacac9) will decrease coverage by 1.77%.
The diff coverage is 12.25%.

❗ Current head f3a6712 differs from pull request most recent head 3739dae. Consider uploading reports for the commit 3739dae to get more accurate results

@@             Coverage Diff              @@
##             master      #63      +/-   ##
============================================
- Coverage     16.45%   14.67%   -1.78%     
- Complexity      241      415     +174     
============================================
  Files            37       51      +14     
  Lines           772     1329     +557     
============================================
+ Hits            127      195      +68     
- Misses          645     1134     +489     

Impacted Files	Coverage Δ
src/Client/Bpost/Client.php	0.00% <0.00%> (ø)
src/Client/PostNL/Client.php	0.00% <0.00%> (ø)
...ndencyInjection/Compiler/RegisterFactoriesPass.php	0.00% <0.00%> (ø)
...dencyInjection/Compiler/RegisterHttpClientPass.php	0.00% <0.00%> (ø)
src/Exception/RequestFailedException.php	0.00% <0.00%> (ø)
src/Factory/Bpost/ServicePointQueryFactory.php	0.00% <0.00%> (ø)
src/Factory/PostNL/ServicePointQueryFactory.php	0.00% <0.00%> (ø)
src/Model/Query/Bpost/ServicePointQuery.php	0.00% <0.00%> (ø)
src/Model/Query/PostNL/ServicePointLookup.php	0.00% <0.00%> (ø)
src/Model/Query/PostNL/ServicePointQuery.php	0.00% <0.00%> (ø)
... and 10 more

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[vvasiloi]

@loevgaard could you please give this a try? I really don't want to use a fork forever.