Add spacing between items in "open" lists (#591)

Override wyrm's `... li p:last-child { margin-bottom: 0 }` from .wy-plain-list-disc and .wy-plain-list-decimal.

Fixes #590. (And probably #354.)

Author: medmunds

sass/_theme_rst.sass

@@ -127,6 +127,8 @@
     @extend .wy-plain-list-decimal
   .section ol p, .section ul p
     margin-bottom: $base-line-height / 2
+    &:last-child
+      margin-bottom: $base-line-height
   .line-block
     margin-left: 0px
     margin-bottom: $base-line-height