Fix tasks for new invoke interface

tasks/__init__.py

@@ -1,7 +1,7 @@
 import os
 import sys
 
-from invoke import Collection, ctask
+from invoke import Collection, task as ctask
 
 from . import osx
 from . import linux

tasks/linux.py

@@ -1,6 +1,6 @@
 import os
 
-from invoke import ctask
+from invoke import task as ctask
 
 from util import RESOURCES_DIRECTORY
 

tasks/osx.py

@@ -1,6 +1,6 @@
 import os
 
-from invoke import ctask
+from invoke import task as ctask
 
 from . import util