Pyflame can't profile its own test suite

[eklitzke]

I wanted to Pyflame the Pyflame test suite, but Pyflame exited very early with a 0 status code. I haven't dug into this yet, but just from thinking about it my guess is that when Pyflame becomes the parent of the traced process it's somehow getting notifications from grandchild processes or something, and then the waitid() loop thinks the traced process has exited. In any event, after building Pyflame the following command should not print profiling data until the test suite is actually done running:

./src/pyflame -t py.test tests/

This is tangentially related to #67, if my waitid() theory is true.