Added attachment streaming
Attachments are downloaded to the specified directory when found
Add 'attachments: true' to the configuration object to stream attachments to the script directory
Add 'attachmentOptions: { directory: "attachments/" }' to specify a attachment directory
"attachment" event is emitted when an attachment is found
Added test script
Added attachment streaming to readme
Merge pull request #20 from achannarasappa/master

Attachment downloading