refer to wiki page on git/ssh access denied.
Merge pull request #882 from ontohub/878-refer_to_wiki_on_access_denied

refer to wiki page on git/ssh access denied.
adding task for generating tree of specific ontology

to build the tree manually for one specific ontology
there is now an rake task to do this
changes according to pull request
Merge branch 'staging' into 819-adjust_entity_tree_rake_task