OAS30Validator readonly writeonly fix

[p1c2u]

Fixes #134

[codecov]

Codecov Report

Merging #135 (9be944c) into master (f47ef8e) will increase coverage by 1.40%.
Report is 2 commits behind head on master.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #135      +/-   ##
==========================================
+ Coverage   82.98%   84.38%   +1.40%     
==========================================
  Files           6        6              
  Lines         241      237       -4     
  Branches       50       48       -2     
==========================================
  Hits          200      200              
+ Misses         26       24       -2     
+ Partials       15       13       -2     

Files	Coverage Δ
openapi_schema_validator/_keywords.py	71.31% <100.00%> (+2.26%)	⬆️
openapi_schema_validator/validators.py	100.00% <ø> (ø)