documented the permissions change to have www-data own the sock file, and the supervisor subprocess *.conf files
Many modifications to supervisor setup section to reflect improved understanding of how to set up for apache without resorting to 777 permissions on the supervisor.sock file.  Fixes #225
This change ensures that the twitterfilter supervisor config files written by SFM will have group write permissions enabled.  This is needed to avoid permission denials when files were written by apache-deployed instance but later a runserver-deployed instance attempts to modify.
Added clarification around the chmod line in supervisor.conf
Merge pull request #263 from gwu-libraries/t225-doc-sock-permission

Supervisor instructions updated, Fixes #225