Revamp button: rename .btn-default to .btn-secondary, drop .btn-info

less/buttons.less

@@ -32,7 +32,6 @@
   &:hover,
   &:focus,
   &.focus {
-    color: @btn-default-color;
     text-decoration: none;
   }
 
@@ -57,25 +56,18 @@
 // Alternate buttons
 // --------------------------------------------------
 
-.btn-default {
-  .button-variant(@btn-default-color; @btn-default-bg; @btn-default-border);
-}
 .btn-primary {
   .button-variant(@btn-primary-color; @btn-primary-bg; @btn-primary-border);
 }
-// Success appears as green
+.btn-secondary {
+  .button-variant(@btn-secondary-color; @btn-secondary-bg; @btn-secondary-border);
+}
 .btn-success {
   .button-variant(@btn-success-color; @btn-success-bg; @btn-success-border);
 }
-// Info appears as blue-green
-.btn-info {
-  .button-variant(@btn-info-color; @btn-info-bg; @btn-info-border);
-}
-// Warning appears as orange
 .btn-warning {
   .button-variant(@btn-warning-color; @btn-warning-bg; @btn-warning-border);
 }
-// Danger and error appear as red
 .btn-danger {
   .button-variant(@btn-danger-color; @btn-danger-bg; @btn-danger-border);
 }