[Speed] perf 0.7.3 released

[Victor Stinner]

The Python perf module is a toolkit to write, run, analyze and modify
benchmarks:
http://perf.readthedocs.io/en/latest/

Version 0.7.3 (2016-08-17):

* add a new ``slowest`` command
* convert: add ``--extract-metadata=NAME``
* add ``--tracemalloc`` option: use the ``tracemalloc`` module to track
  Python memory allocation and get the peak of memory usage in metadata
  (``tracemalloc_peak``)
* add ``--track-memory`` option: run a thread reading the memory usage
  every millisecond and store the peak as ``mem_peak`` metadata
* ``compare_to``: add ``--group-by-speed`` (``-G``) and ``--min-speed`` options
* metadata: add ``runnable_threads``
* Fix issues on ppc64le Power8

Victor