new implementation based on varints

Author: Araq

README.md

@@ -13,6 +13,6 @@ nim c -r -d:release -d:useStdlib benchmark.nim
 On my machine, I got these results:
 
 ```
-packed json:  used Mem: 140.063MiB time: 3.127s
+packed json:  used Mem: 94.06MiB time: 2.622s
 stdlib json:  used Mem: 1.277GiB time: 3.759s
 ```

bench/benchmark.nim

@@ -3,14 +3,15 @@
 when defined(useStdlib):
   import json
 else:
-  import packedjson
+  import ".." / packedjson
 import strutils, times
 
 proc main =
   let jobj = parseFile("1.json")
 
   let coordinates = jobj["coordinates"]
   let len = float(coordinates.len)
+  doAssert coordinates.len == 1000000
   var x = 0.0
   var y = 0.0
   var z = 0.0
@@ -31,7 +32,8 @@ echo "used Mem: ", formatSize getOccupiedMem(), " time: ", cpuTime() - start, "s
 #[
 Results on my machine:
 
-packed json:  used Mem: 140.063MiB time: 3.127s
+packed json:  used Mem: 94.06MiB time: 2.622s
+old version:  used Mem: 140.063MiB time: 3.127s
 stdlib json:  used Mem: 1.277GiB time: 3.759s
 
 ]#