hemokit data has higher time stdev than emokit

I've taken some rough measurements of how long `emokit_read_data_timeout` and `hemokit-dump`'s main loop take per iteration.

For this I modified:

``` c
int emokit_read_data_timeout(struct emokit_device* s, unsigned timeout)
{
static uint64_t t_before = 0;
struct timeval tv;
gettimeofday(&tv, NULL);
uint64_t t = ((uint64_t) tv.tv_sec)*1000000 + (uint64_t) tv.tv_usec;
fprintf(stderr, "%lu\n", t - t_before);
t_before = t;
return hid_read_timeout(s->_dev, s->raw_frame, 32, timeout);
}
```

Results (times in microseconds):

| | emokit (gettimeofday) | hemokit (getCurrentTime) |
| --- | --- | --- |
| mean | 7818.57 | 7662.45 |
| std | 410.32 | 725.25 |
| std/mean | ~5.2 % | 9.5 % |

So the distance between time measurements varies quite a bit more in Hemokit.

This wasn't measured properly though on the Hemokit side; for it to be a fair comparison, I should measure how long `readEmotivRaw` takes, not the time of a `hemokit-dump` loop.