Update "or" to "and" when listing React optimizations (#302)

`shouldComponentUpdate` needs to be used in conjunction with immutable data for fully optimized rendering

Author: chrisvfritz

src/guide/comparison.md

@@ -28,7 +28,7 @@ First, the internal implementation is fundamentally different. React's rendering
 
 The virtual-DOM approach provides a functional way to describe your view at any point of time, which is really nice. Because it doesn't use observables and re-renders the entire app on every update, the view is by definition guaranteed to be in sync with the data. It also opens up possibilities to isomorphic JavaScript applications.
 
-Instead of a Virtual DOM, Vue.js uses the actual DOM as the template and keeps references to actual nodes for data bindings. This limits Vue.js to environments where DOM is present. However, contrary to the common misconception that Virtual-DOM makes React faster than anything else, Vue.js actually out-performs React when it comes to hot updates, and requires almost no hand-tuned optimization. With React, you need to implement `shouldComponentUpdate` everywhere or use immutable data structures to achieve fully optimized re-renders.
+Instead of a Virtual DOM, Vue.js uses the actual DOM as the template and keeps references to actual nodes for data bindings. This limits Vue.js to environments where DOM is present. However, contrary to the common misconception that Virtual-DOM makes React faster than anything else, Vue.js actually out-performs React when it comes to hot updates, and requires almost no hand-tuned optimization. With React, you need to implement `shouldComponentUpdate` everywhere and use immutable data structures to achieve fully optimized re-renders.
 
 API-wise, one issue with React (or JSX) is that the render function often involves a lot of logic, and ends up looking more like a piece of program (which in fact it is) rather than a visual representation of the interface. For some developers this is a bonus, but for designer/developer hybrids like me, having a template makes it much easier to think visually about the design and CSS. JSX mixed with JavaScript logic breaks that visual model I need to map the code to the design. In contrast, Vue.js pays the cost of a lightweight data-binding DSL so that we have a visually scannable template and with logic encapsulated into directives and filters.