Update to 0.6.4.

* Release 0.6.4 (18-Jun-2012)

** Minor Changes

The unreliable 'extras_require' property in setup.py, which allowed other
python programs to declare a dependency on foolscap's "secure_connections"
feature, was removed. See README.packagers for alternate instructions. (#174)

'flogtool' log-dumping commands (dump, tail, web-viewer) now accept a
consistent --timestamps= argument to control how event times are displayed
(UTC, local, seconds-since-epoch, etc). (#192, #193)

Certain invalid "location" strings (accepted by Tub.setLocation and put into
FURLs) are rejected earlier, and with better error messages. The error
message produced when 'flogtool dump' is given a FURL-file (instead of an
event log file) has been improved.

The Incident Gatherer will tolerate incident-file errors better, fetching
remaining incidents instead of halting. (#190)

The git-over-foolscap tools were cleaned up, and the documentation was
brought into line with the implementation. (#197)

Other minor bugs were fixed: #179, #191, #194, #195, #196

(gdt)