add event time column to summarize results

[andjo403]

name it only time for now feel that "incl. time" need more description then only having time and self-time. but feel that the "% of total time" get unclear now that we have time and self-time

closes #107

[wesleywiser]

lgtm, thanks!

[michaelwoerister]

Nice, thanks @andjo403!

One thing I'm wondering? How does this handle recursive invocations like:

       <---A--->
   <------B------>
<---------A--------->

How should it handle cases like this? Always only count the bottom-most stack element?

[andjo403]

as it is now it will count the time for both events in the example see the test https://github.com/rust-lang/measureme/pull/109/files#diff-98cefccab6f8905ece90aaf3c2cb1ea4R479 .
I think that is correct at least that is what I wanted the last time when I want to know how mush time is spent in this event. and feel that it will be strange if the result differs against if it was 3 diffrent events in the stack.

[michaelwoerister]

I think an argument can be made for either way of counting. I think I'm fine with the way it's done here though.