Documentation edits

Edit the documentation for minor grammar, idiomatic usage, and sentence construction issues.  Overall the documentation is great;  this is just cleaning up some places that sound a little odd.

There are some notes left in the documentation delimited by [bwb: ...] where I made a larger-than-usual change or I thought needed attention from someone more familiar with the codebase than I am.


Whit this, I mean that the authenticator will not be updated by the update method if sliding window expiration is disabled. As example: the JWT authenticator does create a new token on every update if it was previously touched. If it wasn't touched then it doesn't create a new token because update will not be executed.