Add recursive merging in APISpec.to_dict

[b0g3r]

In Open API spec 3.0.1 securityDefinitions was renaming and moved to components

APISpec class allowed add additional fields to swagger file with kwarg-parameter options. I try add components with security definition to kwarg, but this rewrite schema definitions (in swagger 3.0.1 schema definitions also in components)

Currently in APISpec.to_dict used dict.update method, but this works without recursion and rewrite nested dict.

How about replace this method to recursive merging (e.g. https://gist.github.com/angstwad/bf22d1822c38a92ec0a9)?

[b0g3r]

May be linked with #165

[fMeow]

I have propose a PR #222 on this issue.

However, I don't think it necessary to recursively update components object. Instead, this issue just happens because apispec would generate a components object with schemas and parameters.

And a simpler way is to merge schemas and parameters, while copying all other fields like 'securitySchemes`.

[sloria]

This is addressed by #222.