V2.0 split bootloader

Note: This was unintentionally branched off of `v2.0-uglify`, which is in PR form.

One case I haven't optimized for is when the scripts are already cached and the bootloader just loads from localstorage. Currently, this will insert this bootloader into the page twice, when it really only needs to be done once. 

I have an idea on how to handle this but I would love some input!

@noahadams please review!