Update options.md documentation to reflect current

[benmccallum]

Addresses issue: #122

[benmccallum]

Hey @pi0 and @breakingrobot,

When updating this documentation, I noticed that here the line const _options = Object.assign({}, this.options.cookie.options, options) seems to merge the entire module options over the module cookie options? Is that intended? Is there a use case for this? Seems like it could case some unintended consequences, not matter how well it's documented.

[pi0]

seems to merge the entire module options over the module cookie options

It only merges cookie related options with an optional 3rd param which is useful for example overriding default expire or cookie's domain.

BTW Thanks for nice enhancements to the docs.