Add new endpoints

[guilyx]

Closes #21
Closes #9

[codecov-commenter]

Codecov Report

Merging #23 (d59894c) into master (34b3914) will decrease coverage by 2.30%.
The diff coverage is 82.70%.

@@            Coverage Diff             @@
##           master      #23      +/-   ##
==========================================
- Coverage   81.54%   79.24%   -2.31%     
==========================================
  Files           8        8              
  Lines         634      660      +26     
==========================================
+ Hits          517      523       +6     
- Misses        117      137      +20     

Impacted Files	Coverage Δ
nexo/client.py	57.14% <23.33%> (-4.82%)	⬇️
nexo/__init__.py	100.00% <100.00%> (ø)
tests/test_api_request.py	100.00% <100.00%> (ø)
tests/test_helpers.py	100.00% <100.00%> (ø)
tests/test_serialized_responses.py	100.00% <100.00%> (ø)

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