Add Error Handling

[cnguy]

It is time to add a few error handlers so that it is more user-friendly (frappe/charts don't handle the errors explicitly sometimes).

Some errors include:

1. Length of a dataset does not equal to length of labels?
2. Length of colors array != length of labels and the length of each dataset?
3. Not passing in a parent string (this does show up in console already)?
4. Update values labels/datasets?
5. Halloween legend colors?
6. Setting the X and Y axis modes?

This also means I should standardize the Render functions so that they return a Chart and Error pair.