Gets an object's information and metadata.
The 'callback' parameter specifies a function which will be called when the operation completes (or an error is encountered). If the 'callback' parameter is not specified, then the method will block and will not return until the operation completes (or an error is encountered).
The callback for this method is defined as:
'err' is the error that occurred. If there was no error, then 'err' is 'null'.
'err' has 2 properties which hold detailed information:
This method gets information and metadata for the object specified by Object in the bucket currently selected by Bucket. If the VersionId property is non-empty, information and metadata for the specified version of the object is retrieved instead.