POC Venmo Button

Should be converted to use our SDK before hitting prod.
Respect Do Not Track header for Segment.io.
Add segment.io testing credentials.
Add segment.io tracking by user id.
Fix segmentio identify functions for anon and auth'd users.
Fix header format for aspen, not django.
Bypass request object modification and check DNT directly from header.
DNT code pushed into util.
Updated privacy policy to mention segment.io.
we don't need a new hook for DoNotTrack
Add a FAQ item about canceling one's account
Add a couple comments to deactivate-final-rename
Rename deactivate-final-rename to cancel

Fits my brain better. Anyone else?
Merge pull request #2369 from gittip/cancel-faq

Add a FAQ item about canceling one's account
Actually, rename cancel to deactivate

Let's say that "deactivate" is a step in the "cancel" process.
Bump version to 12.9.5
Bump version to 12.9.5-dev
Merge pull request #2370 from gittip/cancel-tweaks

Cancel tweaks
Add mention of DNT to privacy policy.
Move account actions into <td> to fix alignment bugs