Support additional params for Flights Pricing Service

• As reported in #15
• Support for the following additional params during poll requests:

            'locationschema',
            'carrierschema',
            'sorttype',
            'sortorder',
            'originairports',
            'destinationairports',
            'stops',
            'outbounddeparttime',
            'outbounddepartstarttime',
            'outbounddepartendtime',
            'inbounddeparttime',
            'inbounddepartstarttime',
            'inbounddepartendtime',
            'duration',
            'includecarriers',
            'excludecarriers'

• Reference doc: http://business.skyscanner.net/portal/en-GB/Documentation/FlightsLivePricingList#pollsession