* Add checkpoint progress tracking for evalute_ppo. Now when specified with a checkpoint directory,
* Evaluate_ppo will evaluate checkpoints in chronological order, and constantly check for new checkpoint.
* Add tensorboard visualization to both train_ppo and evaluate_ppo
* Add video generation for navigation episode evaluation. Generated videos can be either saved locally or visualized through tensorboard.
* Add shortest path visualization

Adds documentation for habitat-api, to view the docs follow instructions in docs/README.md and view the html files from the build folder.

* Builds and installs habitat-sim with python setup.py install
* Added pytorch installation and running habitat baseline test in prediction mode. That maybe too much of testing, but decided to keep it for now.
* Have ideas how to speed up and parallelize jobs. Will follow up in next PRs.
* Run isort and black on whole code to make it happy.
* Includes parallelization of installation steps and use files as flags that step is finished. CircleCI has no good way to parallelize steps and have dependencies one the same machine.
* Cache is used to save conda dependencies installed and build simulator based on commit SHA.

* added conversion of matrix map to color picture
* added example

* static PointGoal sensor, Top Down map measure
* top down map measure

Added collision and proximity measurements; Use is_navigable for a more robust check for top-down map

Benchmark and challenge implementations; PPO agents, Random, ForwardOnly, GoalFollower agents; High resolution top down map and bird-eye visualizations; Collisions measure introduced; SPL success criteria fix; Added deleter that closes subprocesses