v0.16.138

Changes

build: simplify go commands (#2449)
Use ./... instead of loop over packages.
Originally loop over packages was added by #359 that introduced glide package manager.
This manager fetches dependencies into vendor/ subdirectory (see https://glide.readthedocs.io/en/latest/getting-started/) and
apparently loop over packages was necessary back then.
glide usage was removed by #764
The change now also runs testable examples.
Also:

Docker image

Docker image is available in Zalando's Open Source registry:

docker run -it registry.opensource.zalan.do/teapot/skipper:v0.16.138 skipper --help
# arm64
docker run -it registry.opensource.zalan.do/teapot/skipper-arm64:v0.16.138 skipper --help
# arm v7 32bit
docker run -it registry.opensource.zalan.do/teapot/skipper-armv7:v0.16.138 skipper --help