Add file_path option to allow downloading directly to disk
add new exception ShotgunDownloadFileError

Add support for passing in dict to download_attachment()
add new exception ShotgunDownloadFileError
Add support for passing in dict to download_attachment()

backwards compatible so still supports Attachment id.
cleaned up error handling
more tests for download_attachment()
Updated error messages for 403 errors when using download_attachment to access files in S3.
A little bit of clean up for the 403 message.
Merge pull request #43 from shotgunsoftware/22152_support_hash_for_download_attachment

22152 support hash for download attachment (and Pull #32 write directly to disk)