In --filename mode use sys.stdout.

This allows us to capture the output of tinker --draft using backticks.
For example:

    vim $(tinker --draft "Straight to Vim" --filename)

will now work.
Merge pull request #41 from sgillies/master

In --filename mode use sys.stdout.
1.3 release
Merge remote-tracking branch 'upstream/master' into enable-html_link_suffix-spike