sentry: fix env variables docs

fixes gh-506

sentry/content.md

@@ -31,7 +31,7 @@ Sentry is a realtime event logging and aggregation platform. It specializes in m
 4.	If this is a new database, you'll need to run `upgrade`
 
 	```console
-	$ docker run -it --rm -e SENTRY_SECRET_KEY <secret-key> --link sentry-postgres:postgres --link sentry-redis:redis sentry upgrade
+	$ docker run -it --rm -e SENTRY_SECRET_KEY='<secret-key>' --link sentry-postgres:postgres --link sentry-redis:redis sentry upgrade
 	```
 
 	**Note: the `-it` is important as the initial upgrade will prompt to create an initial user and will fail without it**
@@ -39,14 +39,14 @@ Sentry is a realtime event logging and aggregation platform. It specializes in m
 5.	Now start up Sentry server
 
 	```console
-	$ docker run -d --name my-sentry -e SENTRY_SECRET_KEY <secret-key> --link sentry-redis:redis --link sentry-postgres:postgres sentry
+	$ docker run -d --name my-sentry -e SENTRY_SECRET_KEY='<secret-key>' --link sentry-redis:redis --link sentry-postgres:postgres sentry
 	```
 
 6.	The default config needs a celery beat and celery workers, start as many workers as you need (each with a unique name)
 
 	```console
-	$ docker run -d --name sentry-celery-beat -e SENTRY_SECRET_KEY <secret-key> --link sentry-postgres:postgres --link sentry-redis:redis sentry celery beat
-	$ docker run -d --name sentry-celery1 -e SENTRY_SECRET_KEY <secret-key> --link sentry-postgres:postgres --link sentry-redis:redis sentry celery worker
+	$ docker run -d --name sentry-celery-beat -e SENTRY_SECRET_KEY='<secret-key>' --link sentry-postgres:postgres --link sentry-redis:redis sentry celery beat
+	$ docker run -d --name sentry-celery1 -e SENTRY_SECRET_KEY='<secret-key>' --link sentry-postgres:postgres --link sentry-redis:redis sentry celery worker
 	```
 
 ### Port mapping
@@ -58,7 +58,7 @@ If you'd like to be able to access the instance from the host without the contai
 If you did not create a superuser during `upgrade`, use the following to create one:
 
 ```console
-$ docker run -it --rm -e SENTRY_SECRET_KEY <secret-key> --link sentry-redis:redis --link sentry-postgres:postgres sentry createuser
+$ docker run -it --rm -e SENTRY_SECRET_KEY='<secret-key>' --link sentry-redis:redis --link sentry-postgres:postgres sentry createuser
 ```
 
 ## Environment variables