hack to avoid grit call

calling tree to try to determine if a directory exists
exposed this error mojombo/grit#117
hacking a workaround for now to check for the readme using a
method which uses JGit instead

app/models/cite_identifier.rb

@@ -200,11 +200,12 @@ def collection_exists?
 
     path_components << ns
     path_components << coll
+    path_components << "REAMDE.md"
 
-    # e.g. CITE_OAC_XML/perseus/mycoll
+    # e.g. CITE_OAC_XML/perseus/mycoll/README.md
     collection_path = File.join(path_components)
-    tree = self.publication.repository.repo.tree('master', [collection_path])
-    exists = ! tree.contents.first.nil?
+    exists = self.publication.repository.get_file_from_branch(collection_path,'master')
+    exists = ! nil
   end
 
   def to_path