setup.py dependency handling is broken on Ubuntu
- argparse is built-in on py2.7, setup.py tries to install over it.
- boto also available via apt, setup.py tries to install over it too.
So created requirements.txt with boto>=2.0 instead.
Fix error-handling in cmd_send by catching BotoServer error instead of checking message.
Improved logging in cmd_send by printing key=value pairs containing information
about SES parameters, error code, request ID and message ID.
Emitted log message of "timestamp key=value ..." format can be parsed natively by Splunk.