Merge pull request #294 from MITx/jarv/wiki_enabled

reading WIKI_ENABLED from env.json

lms/envs/aws.py

@@ -35,6 +35,7 @@ CACHES = ENV_TOKENS['CACHES']
 for feature,value in ENV_TOKENS.get('MITX_FEATURES', {}).items():
     MITX_FEATURES[feature] = value
 
+WIKI_ENABLED = ENV_TOKENS.get('WIKI_ENABLED',WIKI_ENABLED)
 
 LOGGING = get_logger_config(LOG_DIR, 
                             logging_env=ENV_TOKENS['LOGGING_ENV'],