Adds installation instructions
Fixes a grammatical error

Also, replaces the intended term "air quality" by "air pollution".
Renames calidadaire dir to air-quality
Adds OS X instructions to install scrapy

Also makes some changes in the README
Adds an .editorconfig file
Adds a CHANGELOG file
Replaces "air-quality" ocurrences by "air_quality"

Becase @mostacho :@!
Adds sudo prefix to the pip install command in the README
Merge pull request #1 from chirakiru/better-docs

Better docs