support publishing to local storage (again)

at least with aptly_1.4.0+ds1-4+b4 (found in Debian) doing a simple
"PUT /api/publish/local-repo" or "DELETE /api/publish/local-repo"
will result in a 404.

the proper way is to either use a storage specification ":." or leave it
empty (but keep the slash intact)

Closes: #29

Author: umlaeute

aptly/publisher/__init__.py

@@ -245,7 +245,7 @@ def __init__(self, client, distribution, timestamp=None, recreate=False, load=Fa
 
         self.name = '%s/%s' % (self.prefix or '.', self.distribution)
         self.full_name = "{}{}{}".format(self.storage+":" if self.storage else
-                                         "", self.prefix+"/" if self.prefix else
+                                         "/", self.prefix + "/" if self.prefix else
                                          "", self.distribution)
 
         if not timestamp: