Allow cache to last for a 3 days (apache#136)

Allow all queries cache to last for 3 days by default

@mistercrunch is this overkill?

superset_config.py

@@ -111,7 +111,7 @@ def has_access(self, permission_name, view_name):
 # Caching configuration
 CACHE_CONFIG = {
     'CACHE_TYPE': 'redis',
-    'CACHE_DEFAULT_TIMEOUT': 60 * 60 * 24,
+    'CACHE_DEFAULT_TIMEOUT': 60 * 60 * 24 * 3, 
     'CACHE_KEY_PREFIX': 'superset_',
     'CACHE_REDIS_URL': REDIS_URL,
 }