%time magic

[andrus]

We already started looking to mimic some IPython magics (e.g., see %log). I feel like implementing a version of the %time magic would be useful:

Line magic flavor

%time Csv.load("a.csv");

Cell magic flavor

%%time 
var df = Csv.load("a.csv");
df.cols().merge("concat(a, b)")

The output in IPython is wall time + CPU time:

CPU times: user 1.20 s, sys: 0.05 s, total: 1.25 s
Wall time: 1.37

Wall time is easy. For the CPU times, I suppose we can grab them from ThreadMXBean (and maybe ProcessHandle.Info).