Updated notebooks and tweak code

1. Created new folders (sources, destinations, output_data, matrices, models)
2. Replaced notebooks
3. Added figures
3. Changed code (solving issues)
	- #82: Change syntax to: return self.model_results (Models.py)
	- #84: Do’t return results when calculating the models (Models.py) - I commented it out.
	- #85: focus_categories instead of all_categories (lines 161 and 163 of Models.py)
	- #87: changed plot_type to plot_column (BaseModels.py)

README.md

@@ -74,6 +74,17 @@ Usage
 ---
 See the iPython notebooks in `docs/` for example usage, or https://readthedocs.org/projects/spatial-acccess/ for technical documentation.
 
+Under the **docs** folder, the notebooks run through Chicago's health example:  
+* [reqs.ipynb](./reqs.ipynb)  : This notebook shows the installation and files requirements in order to run the demos.  
+* [matrix.ipynb](./matrix.ipynb)  : This notebook shows how to run the travel time distance matrices.  It uses the [p2p](./scripts/p2p.py) script.
+* [access_score.ipynb](./access_score.ipynb)  : This notebook shows how to run the access score and the specific parameters that might be tweaked depending on the user's interest.  It uses the [ScoreModel](./scripts/ScoreModel.py) and [CommunityAnalytics](./scripts/CommunityAnalytics.py) scripts.
+* [coverage_score.ipynb](./coverage_score.ipynb)  :This notebook shows how to run the coverage score and the specific parameters that might be tweaked depending on the user's interest.  It uses the [ScoreModel](./scripts/ScoreModel.py) and [CommunityAnalytics](./scripts/CommunityAnalytics.py) scripts.
+* [travel_time_metrics.ipynb](./travel_time_metrics.ipynb)  :This notebook shows how to run the travel time distance matrices. It uses the [ScoreModel](./scripts/ScoreModel.py) and [CommunityAnalytics](./scripts/CommunityAnalytics.py) scripts.  
+* [calibration.ipynb](./calibration.ipynb)  : **? Have it as a notebook/within the demos/in this notebook or not at all?** Comparison (validation and calibration) with GoogleMaps.
+
+The **data** folder contains the files needed for the estimation of the metrics under **sources** (for origins) and **destinations** (for destinations). The **matrices** folder contains the estimated symmetric and asymmetric matrices. The **modelss** folder contain the results of the models' analyses. Finally, **figures** contain the results of maps and plots calculated during the process. 
+
+
 ### Overwriting default configuration values
 p2p provides default configuration values for edge weights and node impedence (see spatial_access/configs.py).
 You can overwrite these as follows: