Change donation currency to USD

README.markdown

@@ -40,7 +40,7 @@ You can download CoconutKit from [the official github page](https://github.com/d
 
 CoconutKit is and will stay free. However, if you enjoy using it, you can support the countless hours of work that are invested into its creation. Thank you in advance! 
 
-[![Donate to author](https://www.paypalobjects.com/en_US/i/btn/btn_donate_SM.gif)](https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=3V35ZXWYXGAYG&lc=CH&currency_code=CHF&bn=PP%2dDonationsBF%3abtn_donate_LG%2egif%3aNonHosted)
+[![Donate to author](https://www.paypalobjects.com/en_US/i/btn/btn_donate_SM.gif)](https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=3V35ZXWYXGAYG&lc=CH&currency_code=USD&bn=PP%2dDonationsBF%3abtn_donate_LG%2egif%3aNonHosted)
 
 ### How can I discover CoconutKit components?