Fixup btn-primary when background is used

src/theme.scss

@@ -1988,6 +1988,14 @@ tag-input {
         }
     }
 
+    .btn-primary {
+        background-color: #2196f3c7;
+
+        &:hover {
+            background-color: #2196f3;
+        }
+    }
+
     .input-group-btn {
         .btn-default {
             border-color: #ccc;