Increase max-workers

There's significant speed improvement by having more workers. This
value still shouldn't cause anyone's machines to melt/explode.

Signed-off-by: Mazz Mosley <[email protected]>

compose/const.py

@@ -1,5 +1,5 @@
 
-DEFAULT_MAX_WORKERS = 5
+DEFAULT_MAX_WORKERS = 20
 DEFAULT_TIMEOUT = 10
 LABEL_CONTAINER_NUMBER = 'com.docker.compose.container-number'
 LABEL_ONE_OFF = 'com.docker.compose.oneoff'