Plumb ratchet error messages to the user.

This change causes error messages from the ratchet code to be surfaces
to the user in the contact log. This is to help debug #124.
Note that golang from Ubuntu 14.04 is too old.

When installing on Ubuntu 14.04, Go 1.3 will need to be installed from
source since Ubuntu's is too old now. (Noted in #123.)

See https://golang.org/doc/go1.3#cgo for details of the changes.
Fix crash when deleting home server message.

Fixes #131.
Fixes a bug in moveContactsMessagesToEndOfQueue discussed in #134
Does not resolve the existence of DELIVERY_SIGNATURE_INVALID messages in #134