text: Title: `scanapi-report-example.png` not loading on PyPi description
  Body: ## Description
  
  At [PyPi page desccription](https://pypi.org/project/scanapi/0.0.15/) the image [scanapi-report-example.png](https://github.com/camilamaia/scanapi/blob/master/images/scanapi-report-example.png) is not loading
  
  ![image](https://user-images.githubusercontent.com/2728804/70911530-d71f8280-1ff0-11ea-8f56-85e65b4aec74.png)
  
  This happens because it is being used the relative path to link the image on README.md
  
  How it is now:
  ```
  <p align="center">
    <img src="images/scanapi-report-example.png" width="700">
  </p>
  ```
  
  How it is should be:
  ```
  <p align="center">
    <img src="https://github.com/camilamaia/scanapi/blob/master/images/scanapi-report-example.png" width="700">
  </p>
  ```