This change allows remotes to be created on the fly without a config
file by using the remote type prefixed with a : as the remote name, Eg
:s3: to make an s3 remote.
This assumes the user is supplying the backend config via command line
flags or environment variables.
* Fix remaining problems
* Refactor to make testing easier and add a test suite
* Make path parsing more robust.
* Add single file operations
* Add MimeType reading for objects
* Add documentation
* Note go1.7+ is required to build
