avoid compiler warning in neither cairo or the svg renderer is enabled
support fixed scale_denominator and passing scale_factor to map.renderSync - refs #139
update changelog as per renderSync changes
use latest mapnik-vector-tile@0.2.0
use buffered extent in vector tile datasources to ensure feature filtering is not to aggressive (because mapnik's feature_style_processor will clip by datasource extent)
bump to v1.1.1
merge with master
use the right mapnik-vector-tile branch