Updated baselines readme, fixed links, added link to checkpoints (#126)

README.md

habitat_baselines/README.md

habitat_baselines/__init__.py

habitat_baselines/slambased/README.md

habitat_baselines/slambased/install_deps.sh

habitat_baselines/slambased/mappers.py

habitat_baselines/slambased/monodepth.py

habitat_baselines/slambased/path_planners.py

habitat_baselines/slambased/reprojection.py

habitat_baselines/slambased/utils.py