Update readme and file name (#13)

Author: engai

README.md

@@ -10,7 +10,7 @@ A <a href="https://www.sketchapp.com/">Sketch</a> file of common design patterns
 <h3 align="center"><a href="https://github.com/salesforce-ux/design-system-ui-kit/archive/master.zip">» Download the latest version «</a></h3>
 <br />
 
-[![UI Kit Preview](https://cloud.githubusercontent.com/assets/85783/24780081/69e09d76-1ae9-11e7-8f2b-ea30fc91ec51.jpg)](https://github.com/salesforce-ux/design-system-ui-kit/archive/master.zip)
+[![UI Kit Preview](https://user-images.githubusercontent.com/12544709/34635155-66068cc2-f240-11e7-9043-e6b77b4e5ff4.png)](https://github.com/salesforce-ux/design-system-ui-kit/archive/master.zip)
 
 
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@@ -31,11 +31,11 @@ Download the most recent version of [Sketch](https://www.sketchapp.com/).
 
 ## Contribute!
 
-The SLDS team welcomes your help in maintaining and growing this UI kit. 
+The SLDS team welcomes your help in maintaining and growing this UI kit.
 
 Here are a few of the kinds of contributions we are looking for:
 
-1. **Bug fixes:** fixing goofs in the Sketch file where what it has for a component doesn’t match what we are displaying for that component in the code-based documentation 
+1. **Bug fixes:** fixing goofs in the Sketch file where what it has for a component doesn’t match what we are displaying for that component in the code-based documentation
 2. **New Pattern:** sharing your design for arranging several components into a useful UI widget
 3. **New Template:** sharing a more complex design that contains components and patterns arranged into an entire screen layout