Replace ZeroClipboard with clipboard.js.

Things left:
1. clear the selection after copy
2. add messages for success and error

docs/assets/scss/_clipboard-js.scss

@@ -1,8 +1,8 @@
-// ZeroClipboard
+// clipboard.js
 //
 // Flash-based `Copy` buttons for code snippets.
 
-.zero-clipboard {
+.bd-clipboard {
   position: relative;
   display: none;
   float: right;
@@ -28,7 +28,7 @@
 }
 
 @media (min-width: 768px) {
-  .zero-clipboard {
+  .bd-clipboard {
     display: block;
   }
 }

docs/assets/scss/_component-examples.scss

@@ -75,7 +75,7 @@
   }
 
   + .highlight,
-  + .zero-clipboard + .highlight {
+  + .clipboard + .highlight {
     margin-top: 0;
   }
 

docs/assets/scss/docs.scss

@@ -57,7 +57,7 @@ $bd-info:           #5bc0de;
 @import "team";
 @import "browser-bugs";
 @import "brand";
-@import "zeroclipboard";
+@import "clipboard-js";
 
 // Load docs dependencies
 @import "syntax";