change classname from .btn-dark to .btn-inverse, change use text

less/buttons.less

@@ -108,8 +108,8 @@
 .btn-success:hover,
 .btn-info,
 .btn-info:hover,
-.btn-dark,
-.btn-dark:hover {
+.btn-inverse,
+.btn-inverse:hover {
   text-shadow: 0 -1px 0 rgba(0,0,0,.25);
   color: @white;
 }
@@ -144,8 +144,8 @@
 .btn-info {
   .buttonBackground(#5bc0de, #2f96b4);
 }
-// Dark appears as black
-.btn-dark {
+// Inverse appears as dark gray
+.btn-inverse {
   .buttonBackground(#454545, #262626);
 }