Add option to see duration in history output

[mrloop]

trafficstars

The flag --time was not used a time is already a Command::time method. The flag -d was not used as already used for --date

This is useful for looking at trends in build times

[mrloop]

I can update README after any discussion about flags used

[BanzaiMan]

Could you rebase with master to bring the tests up to date?

And please include a documentation update as well.

Thank you!