WASHINGTON — House Democrats pushed ahead Wednesday with legislation that would ban certain semi-automatic weapons as they considered their most far-reaching response yet to this summer’s spate of mass shootings.Democrats hope that the 100-page bill moving through the Judiciary Committee will pass the House before the August break. But that is far from assured, with moderates in the party, especially those hailing from politically divided swing districts, wary of a vote on sweeping gun controls ahead of the …