Returns HTTP unauthorized for ajax requests instead of redirecting to the sign-in page

* Implemented flushing interval

When proxying streaming responses, it would not flush the response writer buffer until some seemingly random point (maybe the number of bytes?). This makes it flush every 1 second by default, but with a configurable interval.

* flushing CHANGELOG

* gofmt and goimports

watcher: properly break out in nested blocks

Found via staticcheck:

watcher.go:48:5: ineffective break statement. Did you mean to break out of the outer loop? (SA4011)

* redirect to original path after login

* tests for new redirect behaviour

* fixed comment

* added redirect fix to changelog

OIDC ID Token, Authorization Headers, Refreshing and Verification

Update changelog for Docker Improvements

Docker improvement

Dockerfile.dev is ignored by both git and docker for faster development
cycle of docker build.

Update Dockefile to get a much smaller footprint with alpine image.

Optimize ordering of build steps to avoid needless downloads.

Include CA certificates needed for practical use.

Update Makefile to build a static binary by default.

build: use go 1.11

Release 3.0.0

Migration from Bitly to Pusher