Add support for minimum and maximum

[storey]

This adds support for generating the minimum and maximum swagger keywords.

There are two ways to produce these keywords:

1. Explicitly set a minimum or maximum property in the documentation object

documentation: {
  minimum: 0,
  maximum: 100,
}

2. Set the values property in the documentation object to a numeric range (which matches grape's built in validation for numeric min + max)

documentation: {
  values: 0..100,
}

[storey]

This is not ideal but when I split up this file into two files I found that there were a bunch of existing MethodLength violations within it that we were ignoring, so I figured I would just keep the status quo of the file not being fully rubocop compliant?

Let me know if we should just refactor that whole file to be compliant (and pull the param parser out) in a separate PR

[mscrivo]

looks great! just that one rubocop item to fix.