Minor param serialization and wording fixes

* Explicitly set `explode: false` in an example as the default
  with `style: form` is `explode: true`; the `explode: true`
  example was also left explicit to reduce confusion.
* Tidy up overly conversational (e.g. "our document") language
  that I'd meant to revisit but forgot about.
* Include the Header Object as one of the places where the
  `style` keyword is used (even if it is the simplest case)
* Minor grammar fix.
* Fix a missing space before an RFC reference.