fix activity tests to not use values_list
switched object_id to int in generic relationships
fixed tests that were looking at query sets in a particular order
commented 500 statuses back in
Fixes #75
added instructions for postgres install and cleanup command
Merge branch 'master' of https://github.com/adlnet/ADL_LRS into postgres
clarified markdown files
Merge pull request #76 from ljwolford/postgres

Postgres
Merge pull request #77 from ljwolford/postgres

Fixes #75
Merge pull request #78 from ljwolford/postgres

Postgres
merge master