Add build tool

[benmccann]

It'd make sense to have the chart type and scale in different files that get combined together using gulp rather than trying to put everything in a single file.

For an example you can see:
https://github.com/benmccann/Chart.Financial.js

[benmccann]

This would be fixed by using Scott's code, which supports Chart.js v2: https://github.com/scottmcculloch/Chart.LinearGauge.js