🔥Docker and environment variables cleanup (#270)

* Added dotenv-rails gem to manage environment variables

* Added dotenv-rails gem to manage environment variables
* Removed figaro which was used earlier for this purpose

* Standardized variable names

* Changed all env variables to be upper case. This included changes in files referencing env variables.
* Added example env file with all variables set to empty value
* Removed the earlier setup of copying application.yml and database.yml and the scripts and documentation associated to this

* Docker setup

* Added docker file for building the docker images
* Added entrypoint.sh script which is referenced inside the Docker image
* Cloned the Procfile for development using docker which has slight change compared to regular procfile
* Added the docker-compose.yml which has 3 service's configuration, postgres, redis and chatwoot server and a mounted volume for postgres

* Added docker related info to documentation

* Added the docker setup info in the documentation
* Added info for using`rbenv` instead of rvm for managing ruby versions
* Updated the documentation for environment variables to have one about `dotenv-rails` gem and removed the documentation about the old copy paste method used by figaro

* Changing the postgres database, username and password as environment variables

* Removed database.yml from gitignore
* Made the postgres databse, username and password as environemnt variables
* Added this in documentation

* Added a quick setup page

* Added quick setup page
* Removed the docs from README and added link to the docs in website
* Removed the figaro related things from circle.ci config

* Adding external volume for redis in docker compose

* Added instructions for adding the redis volume in docs

app/controllers/api/v1/callbacks_controller.rb

@@ -53,7 +53,7 @@ class Api::V1::CallbacksController < ApplicationController
   end
 
   def long_lived_token(omniauth_token)
-    koala = Koala::Facebook::OAuth.new(ENV['fb_app_id'], ENV['fb_app_secret'])
+    koala = Koala::Facebook::OAuth.new(ENV['FB_APP_ID'], ENV['FB_APP_SECRET'])
     long_lived_token = koala.exchange_access_token_info(omniauth_token)['access_token']
   end