Implement AUTH. Closes #58

This change makes password authentication required
for redis usage, and removes anonymous access. Users
will need to change their underlying clients to enable
writing the auth token for authenticating, otherwise
requests will fail.

This is a non-optional change, and improves security
for users who wish to expose their redis installations
outside of their network.

tests/service_export.bats

@@ -25,6 +25,7 @@ teardown() {
   export ECHO_DOCKER_COMMAND="true"
   export SSH_TTY=`tty`
   run dokku "$PLUGIN_COMMAND_PREFIX:export" l
+  password="$(cat "$PLUGIN_DATA_ROOT/l/PASSWORD")"
   assert_exit_status 0
   assert_output "docker exec dokku.redis.l cat /data/dump.rdb"
 }
@@ -33,6 +34,7 @@ teardown() {
   export ECHO_DOCKER_COMMAND="true"
   unset SSH_TTY
   run dokku "$PLUGIN_COMMAND_PREFIX:export" l
+  password="$(cat "$PLUGIN_DATA_ROOT/l/PASSWORD")"
   assert_exit_status 0
   assert_output "docker exec dokku.redis.l cat /data/dump.rdb"
 }