[20160811151210] General Enhancements

[ddollar]

NOTICE: This release contains an update to the ECS AMIs. Please test carefully for undesired behavior before upgrading.

• #1014 update ecs amis [@ddollar]
• #1015 cache identical builds [@ddollar]
• #1017 update convox/proxy during cli update [@ddollar]
• #1022 fix for building from symlink dirs [@ddollar]
• #1025 use bundle exec for assets:precompile in the rails template [@ddollar]