dropping support for shapefiles, roads

[jGaboardi]

This PR:

• Addresses .shp read needed? #46
• Addresses Only TIGER/Line Edges? #47
• Beefs up docs, etc

[codecov]

Codecov Report

Merging #48 (075cf9b) into main (0f561a1) will increase coverage by 0.7%.
The diff coverage is 100.0%.

@@           Coverage Diff           @@
##            main     #48     +/-   ##
=======================================
+ Coverage   85.8%   86.5%   +0.7%     
=======================================
  Files          5       5             
  Lines       1337    1309     -28     
  Branches     342     333      -9     
=======================================
- Hits        1147    1132     -15     
+ Misses       122     117      -5     
+ Partials      68      60      -8     

Impacted Files	Coverage Δ
tigernet/tigernet.py	98.0% <100.0%> (+4.5%)	⬆️
tigernet/utils.py	81.1% <100.0%> (-0.1%)	⬇️