Fix responsive columns and rows (#24)

Author: arthurxavierx

src/Lumi/Components/Column.purs

@@ -48,7 +48,7 @@ styles = jss
           , display: "flex"
           , flexDirection: "column"
 
-          , "& @media (max-width: 860px)":
+          , "@media (max-width: 860px)":
               { flexDirection: "row"
               }
           }

src/Lumi/Components/Row.purs

@@ -42,7 +42,7 @@ styles = jss
           , display: "flex"
           , flexDirection: "row"
 
-          , "& @media (max-width: 860px)":
+          , "@media (max-width: 860px)":
               { flexDirection: "column"
               }
           }