Removed all locking on stats updates and introduce 32-bit ARM packed bin

[filipecosta90]

This PR fixes #9 and removes all locking from the benchmark tool.

Removed all locking on stats updates
previous:

$ ./redis-benchmark-go -n 5000000 -c 50 -p 6379 set foo bar
Total clients: 50. Commands per client: 100000 Total commands: 5000000
Using random seed: 12345
                 Test time                    Total Commands              Total Errors                      Command Rate           p50 lat. (msec)
                       31s [100.0%]                   5000000                         0 [0.0%]                 159678.24                      0.30      
#################################################
Total Duration 31.000 Seconds
Total Errors 0
Throughput summary: 161288 requests per second
Latency summary (msec):
          p50       p95       p99
        0.299     0.428     0.626

current:

$ ./redis-benchmark-go -n 5000000 -c 50 -p 6379 set foo bar
Total clients: 50. Commands per client: 100000 Total commands: 5000000
Using random seed: 12345
                 Test time                    Total Commands              Total Errors                      Command Rate           p50 lat. (msec)
                       29s [100.0%]                   5000000                         0 [0.0%]                 106459.77                      0.29      
#################################################
Total Duration 29.001 Seconds
Total Errors 0
Throughput summary: 172407 requests per second
Latency summary (msec):
          p50       p95       p99
        0.287     0.369     0.564