updated the _set_database method to use a class variable for the database connection - this way, we don't override the global CI database variable
fixed typo
updating the tests to use _database instead of db
updating to load 'active_group' database if one is not defined
making _database public
Merge pull request #104 from swatkins/master

Use local database variable instead of CI `$this->db`
Merge remote-tracking branch 'upstream/master'

Conflicts:
	core/MY_Model.php