use privacy level variables instead of hard coded integers
refactor the stream scope

create a class method with the same functionality
move all of the security_sql related sql strings into a new method
use the stream class method instead of the scope
placeholder
 refactor the query building to a new method
refactor to use squeel. still need to refactor the limited_sql

#52
more refactoring of the activity model to use squeel

This is generating the same sql as before the refactoring.

#52
Merge pull request #55 from acmetech/refactor_activity_stream

Refactor activity stream