Cleanup post-add-browserify

:fire: to take place after #699:, to be removed once verified not actually needed:

[x] concat task, nojquery/noleaflet no long needed (already done in 6ae2335b3adccaf96ceb5155033779fc657b9262)
[x] index.js old rails manifest?
[x] src-browserify/loader.js
[x] geo/ui/switcher*
[x] test/lib, sinon no longer used in new specs
[x] Rename _Promise to Promise
[x] Review files/classes that declara plain Backbone.Model and Backbone.Collection (eg: geo/geometries.js)
[x] package.json browser/browserify-shim definitions, all used?
[x] Makefile, really necessary nowadays?
[x] scripts dir, e.g. scripts/compress, only be used for cartodbeditor; can be removed/moved?
[x] grunt/, e.g. templates used in core concat, no longer needed (e.g. underscore_no_conflict, version_header etc.).
[x] vendor/reqwest (unused since not supporting core or nojquery bundles anymore)
[x] vendor/mod/torque.uncompressed, now required through torque.js npm bundle?

Out-of-scope/postponed:

~~rm test/demos/~~ :point_right: #715
~~src/ + test/spec (but not src-browserify)~~ :point_right: #758
CartoDB editor also will need to be updated at some point :point_right: cartodb/cartodb#6068

CartoDB / carto.js