Fix README for gym installation (#104)

* Update main README to properly install gym

* Update baseline README for gym install

README.md

@@ -57,6 +57,7 @@ pip install -e .
 The command above will install only habitat core API. To include habitat_baselines along with all additional requirements, use the command below instead:
 ```bash
 cd habitat-api
+pip install -r requirements.txt
 python setup.py develop --all # install habitat and habitat_baselines
 ```
 2. Install `habitat-sim` from [github repo](https://github.com/facebookresearch/habitat-sim).

habitat_baselines/README.md

@@ -4,6 +4,7 @@ baselines
 
 The `habitat_baselines` sub-package is NOT included upon installation by default. To install `habitat_baselines`, use the following command instead:
 ```bash
+pip install -r requirements.txt
 python setup.py develop --all
 ```
 This will also install additional requirements for each sub-module in `habitat_baselines/`, which are specified in `requirements.txt` files located in the sub-module directory.