grid.sass in bulma-rails-0.0.15

- old
+ new

@@ -103,9 +103,11 @@
   margin-top: -10px
   &:last-child
     margin-bottom: -10px
   &:not(:last-child)
     margin-bottom: 10px
+  &.is-centered
+    justify-content: center
   &.is-mobile
     display: flex
   &.is-gapless
     margin-left: 0
     margin-right: 0