Added serialize method to collections
Added get_entity_id, connect, disconnect, get_connections, and get_connecting to Entity
USERGRID-77 can't login for newly created user due to NPE
Merge pull request #45 from r3b/php-connections

Php connections
Merge pull request #48 from stliu/USERGRID-77

USERGRID-77 can't login for newly created user due to NPE
hand merge of conflicting work from USERGRID-77 (f564f0)
merged in master