First version of pinboard importer.

Change-Id: I2b06b20b2609981b03103b4a26c9c4633abe8473
Merge "First version of pinboard importer."
Add pinboard importer to unreleased 0.9 release notes

Change-Id: I29111d96f8f375a3ad3dff9c0086c96adfb0de5e
Merge branch 'master' of https://camlistore.googlesource.com/camlistore