Add 'created' event to the 'createChart' function

This adds a new event called 'created', which is triggered once a
chart is finished drawing. This is created for all three charts, and
it returns:

- The type (e.g. 'Chartist.Bar')
- The labels (in the case of Chartist.Pie, seriesGroup)
- The created SVG element
Update 'created' event return object

This changes the 'created' event returned object to send back:

- The bounds
- The chartRect
- The options

Additionally, it keeps the inserted SVG as a returned object.
Merge pull request #81 from drewbarontini/develop

"Created" Event