Explain reserve_time

[Guillaume-Mayer]

I have a hard time understanding the reserve_time option of the parser filter.
If I enable or disable the option, I cannot see any difference.
Also it seems slightly different of keep_time_key but not sure how.

The documentation is very succinct and show no examples.
If this could be improved it would be nice.

Thanks

[kenhys]

I hope that it will help #335

[kenhys]

#335 wes merged.

[Guillaume-Mayer]

That's perfectly explained! Thanks!