Replace ZeroClipboard with clipboard.js (backported from v4).

docs/assets/less/clipboard-js.less

@@ -0,0 +1,39 @@
+// clipboard.js
+//
+// JS-based `Copy` buttons for code snippets.
+
+.bs-clipboard {
+  position: relative;
+  display: none;
+  float: right;
+
+  + .highlight {
+    margin-top: 0;
+  }
+}
+
+.btn-clipboard {
+  position: absolute;
+  top: 0;
+  right: 0;
+  z-index: 10;
+  display: block;
+  padding: .25rem .5rem;
+  font-size: 12px;
+  color: #818a91;
+  cursor: pointer;
+  background-color: transparent;
+  border: 0;
+  border-radius: .25rem;
+
+  &:hover {
+    color: #fff;
+    background-color: #027de7;
+  }
+}
+
+@media (min-width: @screen-sm-min) {
+  .bs-clipboard {
+    display: block;
+  }
+}

docs/assets/less/docs.less

@@ -34,7 +34,7 @@
 @import "glyphicons.less";
 @import "customizer.less";
 @import "brand.less";
-@import "zero-clipboard.less";
+@import "clipboard-js.less";
 @import "anchor.less";
 @import "algolia.less";
 @import "misc.less";

docs/assets/less/examples.less

@@ -50,7 +50,7 @@
 
 // Tweak display of the code snippets when following an example
 .bs-example + .highlight,
-.bs-example + .zero-clipboard + .highlight {
+.bs-example + .bs-clipboard + .highlight {
   margin: -15px -15px 15px;
   border-width: 0 0 1px;
   border-radius: 0;
@@ -68,7 +68,7 @@
     box-shadow: none;
   }
   .bs-example + .highlight,
-  .bs-example + .zero-clipboard + .highlight {
+  .bs-example + .bs-clipboard + .highlight {
     margin-top: -16px;
     margin-right: 0;
     margin-left: 0;
@@ -76,6 +76,10 @@
     border-bottom-right-radius: 4px;
     border-bottom-left-radius: 4px;
   }
+  .bs-example + .bs-clipboard .btn-clipboard {
+    top: -15px; // due to padding .bs-example has
+    border-top-right-radius: 0;
+  }
   .bs-example-standalone {
     border-radius: 4px;
   }

docs/assets/less/zero-clipboard.less

@@ -1,33 +0,0 @@
-.zero-clipboard {
-  position: relative;
-  display: none;
-}
-.btn-clipboard {
-  position: absolute;
-  top: 0;
-  right: 0;
-  z-index: 10;
-  display: block;
-  padding: 5px 8px;
-  font-size: 12px;
-  color: #767676;
-  cursor: pointer;
-  background-color: #fff;
-  border: 1px solid #e1e1e8;
-  border-radius: 0 4px;
-}
-.btn-clipboard-hover {
-  color: #fff;
-  background-color: #563d7c;
-  border-color: #563d7c;
-}
-
-@media (min-width: @screen-sm-min) {
-  .zero-clipboard {
-    display: block;
-  }
-  .bs-example + .zero-clipboard .btn-clipboard {
-    top: -16px;
-    border-top-right-radius: 0;
-  }
-}