feat(segment):larger margin only for tab attached segment

This PR corrects #19
@hammy2899 already smelled it somehow by his comment 😄

The related issue was related to tab attached segments, but the fix was applied to all attached segments.
This now had impact in some other (non tab) situations.
Most recognizable when an attached segment is used inside a stretched grid row. (See screenshots below)

I also fixed the same situation for top attached tab segments (it was the same issue, but not mentioned/used)

src/definitions/elements/segment.less

@@ -735,7 +735,7 @@ each(@colors,{
   }
 
   /* Top */
-  .ui[class*="top attached"].segment {
+  .ui.segment[class*="top attached"] {
     bottom: 0;
     margin-bottom: 0;
     top: @attachedTopOffset;
@@ -745,6 +745,9 @@ each(@colors,{
   .ui.segment[class*="top attached"]:first-child {
     margin-top: 0;
   }
+  .ui.tab.segment[class*="top attached"]:first-child {
+    margin-top: @verticalMargin;
+  }
 
   /* Bottom */
   .ui.segment[class*="bottom attached"] {
@@ -756,6 +759,9 @@ each(@colors,{
     border-radius: 0 0 @borderRadius @borderRadius;
   }
   .ui.segment[class*="bottom attached"]:last-child {
+    margin-bottom: 0;
+  }
+  .ui.tab.segment[class*="bottom attached"]:last-child {
     margin-bottom: @verticalMargin;
   }
 }