Added std::error::Error::source

[VictorKoenders]

Closes #528

Also made the error naming scheme more consistent

[codecov]

Codecov Report

Merging #530 (249cd96) into trunk (18de104) will decrease coverage by 0.26%.
The diff coverage is 18.75%.

@@            Coverage Diff             @@
##            trunk     #530      +/-   ##
==========================================
- Coverage   71.16%   70.90%   -0.27%     
==========================================
  Files          47       47              
  Lines        3198     3210      +12     
==========================================
  Hits         2276     2276              
- Misses        922      934      +12     

Impacted Files	Coverage Δ
src/error.rs	0.00% <ø> (ø)
src/features/impl_std.rs	75.00% <7.69%> (-4.89%)	⬇️
src/features/impl_alloc.rs	90.43% <50.00%> (-0.80%)	⬇️
src/de/impls.rs	78.39% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 18de104...249cd96. Read the comment docs.