supervisor/http.py: Allow request and file gc

Make tail_f_producer have weakref to request.
Add tail_f_producer.__del__ that closes file.
Merge pull request #392 from msabramo/feature.py3.allow_request_and_file_to_be_garbage_collected

[feature.py3] supervisor/http.py: Allow request and file gc
Make tests not create std{out,err}_logfile in cwd

by modifying 3 tests to use instance.std{out,err}_logfile which are temp
files.

This is an alternative solution to the issue mentioned in #382, #377,
and #417.

Conflicts:
	supervisor/tests/test_options.py