Modifiers::Querying#set_ivars -> #reset_ivars

Slightly more descriptive, and closes a rubocop style violation
`command` causes a method to return `self`

This was prompted by one point of a coworker's summary of Jim Gay's talk
at RubyConf this year.  He said something to the effect that by default,
you should ensure sure no one depends on a method's return value by
having it return `self`.  It immediately occurred to me that this was
much kinder than spreading nils, and might even encourage fluent
interfaces.
TODO: wikipedia "converse"