Add support for RFC 4043 and RFC 7585

[russhousley]

Add module and test for RFC 4043 and RFC 7585

[codecov-io]

Codecov Report

Merging #104 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #104      +/-   ##
==========================================
+ Coverage   99.37%   99.37%   +<.01%     
==========================================
  Files          95       97       +2     
  Lines        5941     5967      +26     
==========================================
+ Hits         5904     5930      +26     
  Misses         37       37

Impacted Files	Coverage Δ
pyasn1_modules/rfc4043.py	100% <100%> (ø)
pyasn1_modules/rfc7585.py	100% <100%> (ø)

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[etingof]

Thank you!