String#underscore isn't particularly slow, but it's possible for us to
call it many times in a users autocomplete request, with mostly-static
values ('User', 'Group', etc.). We can memoise this and save a
surprising amount of time (around 10% of the total request time in some
cases).
The `#reload` makes to load all objects into memory,
and the main purpose of `#reload` is to drop the association cache.
The `#reset` seems to solve exactly that case.
