Fix urinorm - return plain sub delimiters in path

[ziima]

Reduce the strictness of percent encoding in path of urinorm as reported in #41

[codecov-commenter]

Codecov Report

Merging #43 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master      #43   +/-   ##
=======================================
  Coverage   89.48%   89.49%           
=======================================
  Files          93       93           
  Lines       12015    12019    +4     
  Branches     1084     1084           
=======================================
+ Hits        10752    10756    +4     
  Misses       1094     1094           
  Partials      169      169           

Impacted Files	Coverage Δ
openid/test/test_urinorm.py	100.00% <100.00%> (ø)
openid/urinorm.py	91.20% <100.00%> (ø)

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[tpazderka]

LGTM, so waiting for confirmation from #41.

[cjwatson]

Thanks! Can this be merged now?