Remove some leftover interface types

AddDataPoint/AppendDataPoint now use float arrays

Remove all []interface{} types

0.0.3

v0.0.3

Update library to work with frappe/charts@0.0.7

https://github.com/cnguy/gopherjs-frappe-charts/blob/master/CHANGELOG.md

First "release"

This release works with frappe/charts v0.0.4.