Make subperseus work again

Summary:
RCSS isn't available as a global in webapp, so we now bundle it
ourselves instead of taking it from the global scope.

Note: react-components has always done this, so this isn't
actually as large a change as it sounds; it just means
perseus and react-components can both use RCSS.

!!!!!!!!
Note: you will have to restart your server (or run `make install`)
after checking out this version
!!!!!!!!

Test Plan:
`make subperseus`
load http://localhost:8080/math/recreational-math/puzzles/lights-puzzles/e/lights-puzzles-x-3?mp-r-id=PvO6sfU=

`make server`
load http://localhost:9000/test.html

Auditors: charlie, joel