Initial program skeleton

Basic framework for program with argument parsing and basic checks.
Do perf_event_open syscall

Most of the actual code is making sure the perf_event_attr structure is
set up correctly and does everything that it needs.
Write event data from mmap buffer into file

This is the code necessary to write data from the ring buffer used by
perf_event_open() into a file for later use.  One interesting annoyance
of note is that the inherit bit in the perf_event_attr structure CANNOT
be set if you intend to use the mmap interface.  For reasons that are
not entirely clear to your frustrated commit message author.
Update README

Reflect reality and talk about how this came to be and what it's doing
here.