Apply sub-request route's params to the created document if matching the schema

Fixes #354
Merge branch 'sub-resource-post-sets-routes-fields' of github.com:rs/eve into rs-sub-resource-post-sets-routes-fields
flake8 magic
Apply sub-request route's params to new documents.
Merge branch 'rs-sub-resource-post-sets-routes-fields' into develop
Ensure all errors returns a parseable body

Returns parsable (either JSON or XML) body in case of error with status
and error information.

Fixes #365
Add missing HEAD header to list of read method to role access checking
Docstrings and flake8 fixes
Ensure all errors return a parseable body
Merge branch 'rs-parseable-errors' into develop
Merge pull request #367 from rs/fix-missing-read-role-method

Add missing HEAD header to list of read method to role access checking