Erlang PostgreSQL Connection Pool

* Application

  epgsql_pool will create any pools defined in the application's 'pools' environment
  parameter, which is a list of atoms. Each atom must refer to an environment parameter
  with the same name and value {Size, Opts} where Opts is a property list with the
  following supported options:

  host      - host to connect to, default "localhost".
  port      - port to connect to, default 5432.
  username  - username to authenticate with, default os:getenv("USER").
  password  - password to authenticate with, default "".
  database  - database to connect to, no default.

  .config file example:

    {epgsql_pool,  [{pools, [db1, db2]},
                    {db1, {10, [{database, "db1"}]}},
                    {db2, {10, [{database, "db2"}]}}]}                    
  
* Pool Usage

  {ok, C} = pgsql_pool:get_connection(Pool, Timeout).

  Pool          - Pid or Name of pool.
  Timeout       - Time, in milliseconds, to wait for a free connection.

  ok = pgsql_pool:return_connection(Pool, Connection).

* Details

  epgsql_pool monitors the process which called get_connection and returns the
  allocated connection to the pool if that process dies. If a connection dies,
  a new one is created and added to the pool in its place.