ENH: more granularity in example handling

[sjsrey]

Address #485

[codecov]

Codecov Report

Merging #486 (2a9ee94) into master (dc2fe30) will decrease coverage by 0.1%.
The diff coverage is 78.0%.

@@           Coverage Diff            @@
##           master    #486     +/-   ##
========================================
- Coverage    79.3%   79.2%   -0.1%     
========================================
  Files         121     121             
  Lines       12995   13016     +21     
========================================
+ Hits        10307   10315      +8     
- Misses       2688    2701     +13     

Impacted Files	Coverage Δ
libpysal/examples/builtin.py	89.7% <ø> (ø)
libpysal/examples/base.py	60.0% <61.9%> (-4.4%)	⬇️
libpysal/examples/__init__.py	66.7% <88.9%> (-27.9%)	⬇️
libpysal/examples/remotes.py	95.8% <100.0%> (ø)
libpysal/examples/tests/test_available.py	95.3% <100.0%> (+1.1%)	⬆️
libpysal/_version.py	40.7% <0.0%> (+2.7%)	⬆️