Add ENVIRONMENT to vars containers get

This is in support of these tickets:

* freezingsaddles/freezing-nq#4
* freezingsaddles/freezing-sync#14
* freezingsaddles/freezing-web#131

Having an environment variable is a practice I've used in so many places
and I want it here too.

docker-compose.yml

@@ -146,6 +146,7 @@ services:
       - beanstalkd:beanstalkd.container
       - datadog:datadog.container
     environment:
+      ENVIRONMENT: ${ENVIRONMENT}
       DEBUG: ${DEBUG}
       BEANSTALKD_HOST: beanstalkd.container
       BEANSTALKD_PORT: 11300
@@ -177,6 +178,7 @@ services:
     links:
       - beanstalkd:beanstalkd.container
     environment:
+      ENVIRONMENT: ${ENVIRONMENT}
       VIRTUAL_HOST: ${FREEZING_NQ_FQDN}
       LETSENCRYPT_HOST: ${FREEZING_NQ_FQDN}
       LETSENCRYPT_EMAIL: ${LETSENCRYPT_EMAIL}
@@ -199,6 +201,7 @@ services:
     links:
       - beanstalkd:beanstalkd.container
     environment:
+      ENVIRONMENT: ${ENVIRONMENT}
       VIRTUAL_HOST: ${FREEZING_WEB_FQDN}
       LETSENCRYPT_HOST: ${FREEZING_WEB_FQDN}
       LETSENCRYPT_EMAIL: ${LETSENCRYPT_EMAIL}

example.env

@@ -1,3 +1,7 @@
+# freezing-compose .env file
+# See https://github.com/freezingsaddles/freezing-compose
+
+#
 # MySQL Settings - for freezing-mysql container
 # ---------------------------------------------
 #
@@ -23,6 +27,9 @@ MYSQL_PORT=3306
 # Title for the competition
 COMPETITION_TITLE=Freezing Saddles
 
+# Put your environment name here - e.g. "production", "staging", "localdev"
+ENVIRONMENT=sample
+
 # Flask session keying secret key. Set it to something unique, for example:
 #  python -c 'import uuid; print(uuid.uuid4())'
 SECRET_KEY=deadbeef