Issue #114: Track execution time and print it out in debug statements.

This is just the beginning of this work.. but its a simple wrapper for
now to track the execution time of every actor and log it to a debug log
statement. In the future we can add optional printing of these
statements, global statistic tracking, and even some kind of reporting
at the end with the stats.
Merge pull request #133 from Nextdoor/issue_114

Issue #114: Track execution time and print it out in debug statements.