Install dependencies in start-app.sh

This shell script is used by the pp-development directory to start the app.
When an external user runs this script for the first time, we should install
dependencies for them rather than exploding. This will be a no-op if the
deps are installed already.
Remove instruction to install supervisor

This is handled by npm install as of d959a62c072935bb6f6657c902f8f5e318b192af.
Our graphs throw a javascript exception if you mouse outside of the graph shown.
This fix just sets the available hover region to be exactly that of the graph.
[Finishes #64655760]
Merge pull request #185 from alphagov/improve-start-app

Install dependencies in start-app.sh
Merge pull request #190 from alphagov/bugfix/graphHover

Our graphs throw a javascript exception if you mouse outside of the graph.
Always show all ticks on sparkline graphs, where present
Use Backbone "on" for all events
Merge branch 'master' of github.com:alphagov/spotlight into sparkline-for-real-time-module