Changing columns prop no longer updates state after 2.0.0

## Expected Behavior

Changing the columns prop should update the internal column state and render the new columns. This was working in 2.0.0.

## Current Behavior

The columns stay the same after updating the prop.

## Steps to Reproduce (for bugs)

1. Create an initial table
2. Add a new column to the columns prop
3. Table does not render the new column

## Your Environment

| Tech | Version |
|--------------|---------|
| Material-UI | 3.9.3 |
| MUI-datatables | 2.2.0 |
| React | 16.8.6 |