Implement collectors

[rgreinho]

Description

A collector is an object having the ability to collect information from a specific provider (i.e. 'yelp' or 'google').

Miscellaneous items:

• Update .gitignore file
• Update Makefile
• Update test dependencies:
  • Add Faker
  • Add pytest-mock
• Update Sphinx documentation structure
• Update the documentation
• Use the basicstrap sphinx theme for the documentation
• Add unit tests
• Fix tox.ini
• Fix coala
  • The output is broken in the pre version (see https://github.com/coala/coala/pull/4420 for more details)
• Ensure the ci-* targets are passing

Motivation and Context

This patch implements a Google and a Yelp collector as well as a generic client collector which abstracts all the mechanisms to authenticate and retrieve the exact information we want.

How Has This Been Tested?

Mostly by hand, but implements a few basic unit tests that will be enhanced in the future.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [X] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [X] My change requires a change to the documentation.
• [X] I have updated the documentation accordingly.