fix(Select): Select placeholder color

Update Select placeholder color from 999 to ccc

#204

src/common/stylus/theme/default.styl

@@ -187,7 +187,7 @@ $select-disabled-bgc := $color-light-grey-opacity
 $select-border-color := $color-light-grey-s
 $select-border-active-color := $color-orange
 $select-icon-color := $color-light-grey
-$select-placeholder-color := $color-light-grey
+$select-placeholder-color := $color-light-grey-s
 
 // swipe
 $swipe-btn-color := $color-white