spike: npx pepr -- how do we update the version?

[btlghrants]

Personal experience -- and Issues like #530 -- have shown that the way NPX deals with versions of installed binaries tends to surprise people:

• npx pepr installs the most recent version available
• npx pepr@version will install the requested (potentially newer) version
• npx pepr --version (i.e no version tag) will show that npx still uses the older, origninally installed version.

Our answer (i.e. #530) is to instruct people to clear their machine's .npm cache (i.e. where npx installs things), but... maybe there's a better way?

It would be nice if there was a command that users could run (sort of like npx pepr update) that would install & relink a newer npx pepr-able version.