Update leaflet-search to unrequire Leaflet component

Pulls fix for stefanocudini/leaflet-search#44.
Move to Jake as build system

Jake, unlike Grunt, supports task dependencies, which we definitely
are in need of, so things like 8c890ca don't happen again.
Group Leaflet modules in .gitmodules
Simplify the build config example

People should already get it's executable code from the rest of the
file.
Add a `serve` task

Turns out it's possible to have two background tasks (`watch` and
`serve`), making this actually useful for live development.