Add swig back into the openmm conda build requirements.
Add swig back into the openmm conda build requirements.


Former-commit-id: f32aaa6a405a524cf6aa1414e1ddb2cd3d6fb989
marscher/omnia-conda-recipes,cwehmeyer/conda-recipes,danielparton/omnia-md-conda-recipes,omnia-md/conda-recipes,cwehmeyer/conda-recipes,rmcgibbo/conda-recipes,jchodera/conda-recipes,rmcgibbo/conda-recipes,omnia-md/conda-recipes,rmcgibbo/conda-recipes,jchodera/conda-recipes,cwehmeyer/conda-recipes,jchodera/conda-recipes,peastman/conda-recipes,mpharrigan/conda-recipes,omnia-md/conda-recipes,danielparton/omnia-md-conda-recipes,rmcgibbo/conda-recipes,cwehmeyer/conda-recipes,marscher/omnia-conda-recipes,swails/conda-recipes,peastman/conda-recipes,marscher/omnia-conda-recipes,mpharrigan/conda-recipes,mpharrigan/conda-recipes,marscher/omnia-conda-recipes,swails/conda-recipes,jchodera/conda-recipes,swails/conda-recipes,swails/conda-recipes,peastman/conda-recipes