Add the AWS-generated message_id to the ruby message object
Add suffix to message_id
Make sure raw_message responds to message_id before setting it
Merge branch 'master' into add-message-id-to-message
Merge branch 'master' into add-message-id-to-message
Added test for setting message id on raw messages.

When calling `AWS::SimpleEmailService#send_raw_message` with an
object that responds to `#message_id=`, then the message ID
from the SES response will be set on the raw message.

Added a missing test and corrected the `#responds_to?` check.

Fixes #261
Change HTTP handler to whitelist network errors

Instead of (dangerously) whitelisting errors to reraise, this changes
the HTTP handler to explicitly list the raised exceptions for which the
exceptions should be swallowed.

Fundamentally, this changes handling of unknown errors (such as any Java
error in JRuby) to not be swallowed.