Re-add keybase plugin after upstream bug fix.
Revert "Removed keybase plugin because it both didn't work and broke frequently."

This reverts commit 68bd058f245dc42b5c8038588e6598b065d0a330.
Re-add tell after upstream bug fix.
Revert "Removed tell because it was replaced by a separate mailbot."

This reverts commit 0a6b7ded32054fb8c9b6e2c903866b08ef85541f.
Updated tell plugin with changes from mailbot.