Use Environment variables

[nbelzer]

Resolves #4

• Removes the config from the template module.

• Introduces environment variables to alter runtime behaviour.

• The env variables are defined and used as follows:

  {
  "name": service_name,
  "database": {
  "type": os.getenv("DB_TYPE", "postgres"),
  "setup": os.getenv("DB_SETUP", False),
   "connection": {
       "host": os.getenv("DB_HOST", "127.0.0.1"),
        "database": os.getenv("DB_IDENTIFIER", service_name),
         "user": os.getenv("DB_USER", ""),
         "password": os.getenv("DB_PASS", "")
  }
  },
  "dev": {
     "host": os.getenv("DEV_HOST", "127.0.0.1"),
     "port": os.getenv("DEV_PORT", 5000)
  }
  }

• Most importantly is the DB_TYPE which can either be postgres or cassandra.

• I've chosen to use DB_IDENTIFIER for both the database for postgres and keyspace for Cassandra.

• Based on feedback from @doudejans I've also added an ENVIRONMENT variable that defaults to development and can be set to production when running in production.

if os.getenv("ENVIRONMENT", "development") == "development":
    config['dev'] = {
    "host": os.getenv("DEV_HOST", "127.0.0.1"),
    "port": os.getenv("DEV_PORT", 5000)
  }