implement parallel collecting. add keen_io reporter. several fixes

metrics/disk_io.sh

@@ -26,7 +26,7 @@ else
 fi
 
 collect () {
-  report $(cat < $__disk_io_fifo)
+  report $(cat $__disk_io_fifo)
 }
 
 terminate () {

metrics/swap.sh

@@ -3,11 +3,12 @@
 if is_osx; then
   collect () {
     report $(sysctl -n vm.swapusage |
-                awk '{ if ($3 == 0) exit; printf "%.1f", $6 / $3 * 100.0 }')
+              awk '{ if (int($3) == 0) exit; printf "%.1f", $6 / $3 * 100.0 }')
   }
 else
   collect () {
-    report $(free | awk '/Swap/{ printf "%.1f", $3/$2 * 100.0 }')
+    report $(free |
+        awk '/Swap/{ if (int($2) == 0) exit; printf "%.1f", $3 / $2 * 100.0 }')
   }
 fi