Node uses the location of index as a starting point when looking for
node_modules. Previously, we always loaded index.html out of the app
bundle, which caused us to always load node_modules from the app
bundle as well, which is not what we want in dev mode. Since we no
longer depend on a compiled require.js, it's just as easy to load
index.html from the repository path when in dev mode.
836ff53ef3