Created multiple series how-to page and closed div in interactive.html

- Created multiple series controller
- Added route to app.routes
Added content to multiple series how-to guide

- Updated multipleseries controller with chart code
Merge pull request #274 from tylerferguson/web-feature/multiple-series-how-to

Added multiple series how-to guide
Factor out chart code from getting started controller
Add axis customisation page with controller

- Add new css rule
- copy of code taken from GettingStartedController
Update working in how-to guide

Also removed how to headings, which do not seem beneficial
to the reader.
Merge pull request #276 from matthewdunsdon/web/feature/axis-customisation

Create axis customisation how to guide