Merged comment test for #34 with existing keyframe test.

It appears that each at-rule requires it's own "above comment" test
rather than a generic one.

Updating existing tests is less duplication than having dedicated
comment tests.

Author: paulyoung

test/cases/comment.at-rule.css

@@ -1,8 +1,13 @@
 @keyframes fade {
+  /* from above */
   from {
+    /* from inside */
     opacity: 0;
   }
+
+  /* to above */
   to {
+    /* to inside */
     opacity: 1;
   }
 }

test/cases/comment.at-rule.json

@@ -6,68 +6,124 @@
         "type": "keyframes",
         "name": "fade",
         "keyframes": [
+          {
+            "type": "comment",
+            "comment": " from above ",
+            "position": {
+              "start": {
+                "line": 2,
+                "column": 3
+              },
+              "end": {
+                "line": 2,
+                "column": 19
+              }
+            }
+          },
           {
             "type": "keyframe",
             "values": [
               "from"
             ],
             "declarations": [
+              {
+                "type": "comment",
+                "comment": " from inside ",
+                "position": {
+                  "start": {
+                    "line": 4,
+                    "column": 5
+                  },
+                  "end": {
+                    "line": 4,
+                    "column": 22
+                  }
+                }
+              },
               {
                 "type": "declaration",
                 "property": "opacity",
                 "value": "0",
                 "position": {
                   "start": {
-                    "line": 3,
+                    "line": 5,
                     "column": 5
                   },
                   "end": {
-                    "line": 3,
+                    "line": 5,
                     "column": 15
                   }
                 }
               }
             ],
             "position": {
               "start": {
-                "line": 2,
+                "line": 3,
                 "column": 3
               },
               "end": {
-                "line": 4,
+                "line": 6,
                 "column": 4
               }
             }
           },
+          {
+            "type": "comment",
+            "comment": " to above ",
+            "position": {
+              "start": {
+                "line": 8,
+                "column": 3
+              },
+              "end": {
+                "line": 8,
+                "column": 17
+              }
+            }
+          },
           {
             "type": "keyframe",
             "values": [
               "to"
             ],
             "declarations": [
+              {
+                "type": "comment",
+                "comment": " to inside ",
+                "position": {
+                  "start": {
+                    "line": 10,
+                    "column": 5
+                  },
+                  "end": {
+                    "line": 10,
+                    "column": 20
+                  }
+                }
+              },
               {
                 "type": "declaration",
                 "property": "opacity",
                 "value": "1",
                 "position": {
                   "start": {
-                    "line": 6,
+                    "line": 11,
                     "column": 5
                   },
                   "end": {
-                    "line": 6,
+                    "line": 11,
                     "column": 15
                   }
                 }
               }
             ],
             "position": {
               "start": {
-                "line": 5,
+                "line": 9,
                 "column": 3
               },
               "end": {
-                "line": 7,
+                "line": 12,
                 "column": 4
               }
             }
@@ -79,7 +135,7 @@
             "column": 1
           },
           "end": {
-            "line": 8,
+            "line": 13,
             "column": 2
           }
         }