Miniflux 2.0.15

• Move Dockerfile to main repo
• Change location of the binary from /usr/local/bin to /usr/bin in Docker image
• Add double tap detection for next/previous page navigation
• Allow users to disable auto-remove
• Make parser compatible with Go 1.12
• Add Golang 1.12 to CI
• Use feed ID instead of user ID to check entry URLs presence
• Fix typo in stylesheet
• Sort search results by relevance
• Use preferably the published date for Atom feeds
• Add Spanish translation
• Rename session cookies
• Handle the case when application session is expired and not user session