merge from upstream master

* Update Habitat-API to allow for no rendering sensors (facebookresearch#139)

Update Habitat-API to allow for no rendering sensors

* Added installation requirements step for sim installation in CI setup. (facebookresearch#159)

Added installation requirements step for sim installation in CI setup

.circleci/config.yml

@@ -117,11 +117,13 @@ jobs:
               then
                 git clone https://github.com/facebookresearch/habitat-sim.git
                 cd habitat-sim
+                pip install -r requirements.txt --progress-bar off
                 python setup.py install --headless
               else
                 if [ ! -f ~/miniconda/pip_deps_installed ]
                 then
                   cd habitat-sim
+                  pip install -r requirements.txt --progress-bar off
                   python setup.py install --headless
                 fi
               fi

habitat/sims/habitat_simulator/habitat_simulator.py

@@ -189,13 +189,6 @@ def create_sim_config(
             sim_sensor_cfg.sensor_type = sensor.sim_sensor_type  # type: ignore
             sensor_specifications.append(sim_sensor_cfg)
 
-        # If there is no sensors specified create a dummy sensor so simulator
-        # won't throw an error
-        if not _sensor_suite.sensors.values():
-            sim_sensor_cfg = habitat_sim.SensorSpec()
-            sim_sensor_cfg.resolution = [1, 1]
-            sensor_specifications.append(sim_sensor_cfg)
-
         agent_config.sensor_specifications = sensor_specifications
         agent_config.action_space = registry.get_action_space_configuration(
             self.config.ACTION_SPACE_CONFIG