Normalize indentation

Replace mixed tabs and spaces with just tabs, appeasing both jslint and
sensible, space-locing, vim-using coders around the world :+1:
Make infinite scroll optional, minor syntax cleanup

Added config variable with an option (`enable_inf_scroll`) to control
whether infinite scrolling is enabled or not.

(This should eventually have some sort of UI instead of being
hardcoded.)
More cleanup, moving existing settings into config object