adding nocpusum feature (removes cpu row from list) + go fmt 

Hi !
It may looks like a huge change, but it's not.
This is what I changed :
- I did a simple ```go fmt``` run over all go files
- & Added an option to remove ```cpu``` row from list (We can compute global cpu stats from cpu list , and it's way simple when doing statistics over cpu list -> you don't need to explicitly remove cpu row from stats rules)

Previous behaviour is preserved and shouldn't be diffrent :
```
> ./sysinfo_influxdb -c="cpus" -P metrics

#0: metrics.cpu
| id	| user	| nice	| sys	| idle	| wait	| total	|
| cpu	| 8	| 0	| 12	| 773	| 0	| 793	| 
| cpu0	| 5	| 0	| 4	| 90	| 0	| 99	| 
| cpu1	| 0	| 0	| 5	| 94	| 0	| 99	| 
| cpu2	| 1	| 0	| 2	| 94	| 0	| 97	| 
| cpu3	| 1	| 0	| 0	| 97	| 0	| 98	| 
| cpu4	| 0	| 0	| 0	| 99	| 0	| 99	| 
| cpu5	| 0	| 0	| 0	| 100	| 0	| 100	| 
| cpu6	| 1	| 0	| 0	| 98	| 0	| 99	| 
| cpu7	| 0	| 0	| 0	| 100	| 0	| 100	|
```

New option just remove ```cpu``` from list :
```
> ./sysinfo_influxdb -c="cpus" -P metrics --nocpusum

#0: metrics.cpu
| id	| user	| nice	| sys	| idle	| wait	| total	|
| cpu0	| 0	| 0	| 3	| 96	| 0	| 99	| 
| cpu1	| 3	| 0	| 6	| 92	| 0	| 101	| 
| cpu2	| 5	| 0	| 3	| 91	| 1	| 100	| 
| cpu3	| 1	| 0	| 0	| 98	| 0	| 99	| 
| cpu4	| 2	| 0	| 1	| 97	| 0	| 100	| 
| cpu5	| 0	| 0	| 0	| 99	| 1	| 100	| 
| cpu6	| 4	| 0	| 2	| 98	| 0	| 104	| 
| cpu7	| 0	| 0	| 0	| 99	| 0	| 99	| 
```