Relationship lookups form lists to dicts

[jGaboardi]

Addressing #32.

[codecov]

Codecov Report

Merging #33 (dc4d6a0) into main (a6a2733) will decrease coverage by 1.9%.
The diff coverage is 83.3%.

@@           Coverage Diff           @@
##            main     #33     +/-   ##
=======================================
- Coverage   78.3%   76.4%   -1.9%     
=======================================
  Files          5       5             
  Lines        971     986     +15     
  Branches     253     258      +5     
=======================================
- Hits         760     753      -7     
- Misses       150     168     +18     
- Partials      61      65      +4     

Impacted Files	Coverage Δ
tigernet/utils.py	70.0% <82.1%> (-2.5%)	⬇️
tigernet/tigernet.py	88.9% <100.0%> (-0.1%)	⬇️