openapi-framework: fix backslahses problems when on windows

[rossi-p]

This commit solves the problem with windows file system when generating the swagger file with openapi-framework. With this commit the swagger is now generating the docs with ('/') instead of the ('').

[jsdevel]

@rossi-p how is this different from https://github.com/kogosoftwarellc/open-api/pull/869 ?

[rossi-p]

@jsdevel The PR 869 solves the problem when creating the server with Express, but it still generates a Swagger file with paths using backslashes ( \ ).

[renkei]

PR 877 is an alternative PR that modifies the package fs-routes instead of openapi-framework. It also solves the swagger issue mentioned by rossi-p.