Use exclusive time in human output

This commit updates the HumanOutput class to compute summary tables using
the exclusive time of each span. Previously the inclusive time was used
which hid hot spots by causing spans to double-count the runtime of their
children.

Author: Sharpie

profile-parser.rb

@@ -313,11 +313,11 @@ def display(traces)
         trace.each do |span|
           case span.object
           when FunctionSlice
-            span_map[:functions] << span.object
+            span_map[:functions] << span
           when ResourceSlice
-            span_map[:resources] << span.object
+            span_map[:resources] << span
           when OtherSlice
-            span_map[:other] << span.object
+            span_map[:other] << span
           end
         end
       end
@@ -337,13 +337,13 @@ def truncate(str, width)
       end
     end
 
-    def process_group(title, slices)
+    def process_group(title, spans)
       total = 0
       itemized_totals = Hash.new { |h, k| h[k] = 0 }
 
-      slices.each do |slice|
-        total += Integer(slice.time * 1000)
-        itemized_totals[slice.name] += Integer(slice.time * 1000)
+      spans.each do |span|
+        total += span.exclusive_time
+        itemized_totals[span.stack.last] += span.exclusive_time
       end
 
       rows = itemized_totals.to_a.sort { |a, b| b[1] <=> a[1] }