Added catch for unsupported or nonexistent clipboards

Added stdin streaming support, remote filename and mimetype overrides

You can now pipe to rural to upload the pipe contents to S3 and get a
pulic link to that file. If no remote filename override is specified, a
uuid4 filename is created for the file.

Remote filename and mimetypes can now be overridden at runtime.

Bugs relating to empty files have been fixed. This closes $8 and $11.

Fixed bug where verbose output was printed to stdout rather than stderr.

Converted interface to use click library

Fixed bug that broke the AWS credential configuration