docs: Remove reference to blueprints

- These don't exist anymore.
- Fixes #477

README.md

@@ -146,14 +146,6 @@ export default function (defaultOptions) {
 }
 ```
 
-### Generating Chart Components
-
-Ember-highcharts also provides blueprints to easily create sub-classes of the default high-charts component.
-
-```bash
-ember generate chart <chart-name>
-```
-
 ### Obtaining a Reference to the Chart Instance
 
 The `chart` instance is exposed to the yielded content if used in block form: