improve dependencies for image thumbnails and thumbnail component

dist/css/bootstrap.css

@@ -354,6 +354,19 @@ img {
   border-radius: 6px;
 }
 
+.img-thumbnail {
+  display: inline-block;
+  height: auto;
+  max-width: 100%;
+  padding: 4px;
+  line-height: 1.428571429;
+  background-color: #ffffff;
+  border: 1px solid #dddddd;
+  border-radius: 4px;
+  -webkit-transition: all 0.2s ease-in-out;
+          transition: all 0.2s ease-in-out;
+}
+
 .img-circle {
   border-radius: 50%;
 }
@@ -4884,8 +4897,11 @@ a.list-group-item.active > .badge,
   }
 }
 
-.thumbnail,
-.img-thumbnail {
+.thumbnail {
+  display: inline-block;
+  display: block;
+  height: auto;
+  max-width: 100%;
   padding: 4px;
   line-height: 1.428571429;
   background-color: #ffffff;
@@ -4895,22 +4911,12 @@ a.list-group-item.active > .badge,
           transition: all 0.2s ease-in-out;
 }
 
-.thumbnail {
-  display: block;
-}
-
 .thumbnail > img {
   display: block;
   height: auto;
   max-width: 100%;
 }
 
-.img-thumbnail {
-  display: inline-block;
-  height: auto;
-  max-width: 100%;
-}
-
 a.thumbnail:hover,
 a.thumbnail:focus {
   border-color: #428bca;

less/scaffolding.less

@@ -4,7 +4,6 @@
 
 
 // Reset the box-sizing
-// -------------------------
 
 *,
 *:before,
@@ -14,7 +13,6 @@
 
 
 // Body reset
-// -------------------------
 
 html {
   font-size: 62.5%;
@@ -39,7 +37,10 @@ textarea {
   line-height: inherit;
 }
 
-// Reset unusual Firefox-on-Android default style, see https://github.com/necolas/normalize.css/issues/214
+// Reset unusual Firefox-on-Android default style.
+//
+// See https://github.com/necolas/normalize.css/issues/214
+
 button,
 input,
 select[multiple],
@@ -49,7 +50,6 @@ textarea {
 
 
 // Links
-// -------------------------
 
 a {
   color: @link-color;
@@ -68,7 +68,6 @@ a {
 
 
 // Images
-// -------------------------
 
 img {
   vertical-align: middle;
@@ -85,7 +84,19 @@ img {
 }
 
 // Image thumbnails
-// See thumbnails.less for `.img-thumbnail`
+//
+// Heads up! This is mixin-ed into thumbnails.less for `.thumbnail`.
+.img-thumbnail {
+  padding: @thumbnail-padding;
+  line-height: @line-height-base;
+  background-color: @thumbnail-bg;
+  border: 1px solid @thumbnail-border;
+  border-radius: @thumbnail-border-radius;
+  .transition(all .2s ease-in-out);
+
+  // Keep them at most 100% wide
+  .img-responsive(inline-block);
+}
 
 // Perfect circle
 .img-circle {
@@ -94,7 +105,6 @@ img {
 
 
 // Horizontal rules
-// -------------------------
 
 hr {
   margin-top:    @line-height-computed;
@@ -103,9 +113,10 @@ hr {
   border-top: 1px solid @hr-border;
 }
 
+
 // Only display content to screen readers
+//
 // See: http://a11yproject.com/posts/how-to-hide-content/
-// -------------------------
 
 .sr-only {
   position: absolute;

less/thumbnails.less

@@ -3,30 +3,17 @@
 // --------------------------------------------------
 
 
-// Base classes
-// For thumbnail block-level composite components and simple image styles
-
-// The actual thumbnailed element
-// Can be `a`, `div`, or `img`
-.thumbnail,
-.img-thumbnail {
-  padding: @thumbnail-padding;
-  line-height: @line-height-base;
-  background-color: @thumbnail-bg;
-  border: 1px solid @thumbnail-border;
-  border-radius: @thumbnail-border-radius;
-  .transition(all .2s ease-in-out);
-}
+// Mixin and adjust the regular image class
 .thumbnail {
-  display: block;
-}
-.thumbnail > img {
-  .img-responsive();
-}
-.img-thumbnail {
-  .img-responsive(inline-block);
+  .img-thumbnail();
+  display: block; // Override the inline-block from `.img-thumbnail`
+
+  > img {
+    .img-responsive();
+  }
 }
 
+
 // Add a hover state for linked versions only
 a.thumbnail:hover,
 a.thumbnail:focus {