Automatically detect the mime type of served blob
Update the client to recent golib changes
Implement directory support in blob reader
Implement directory structure traversal algorithm.

This allows reading the blob graph as a standard web
structure with pretty relative urls.
Add suffix for directory listing entries.

Note we base on a correct directory mime type here with should be
'application/x-cinode-directory'. This is only important if we want
to show directory listing allowing easy traversal on the data structure.
Directories must end with '/' suffix.
Detect the mimetype from file name (the quick solution for nor) to plese browsers
Redirect if the user did not enter the trailing slash for directory
Can remove the directory suffix generation now, it's not needed anymore.
Fix the usage a bit
Add support for directory index file.

The solution is not the most optimal one but it does it's job.
In the future we may unify mulitple directory scan passes in
order to reduce the serve time.