Release v0.7.0

Changelog

- Add a 'retrieve' filter. Retrieves the full articles from links. Use it like this: retrive(#content). See goquery for queries.
- Bump go to 1.6.0
- Bump mod dependencies to latests versions
- Remove go generate and use the new go embed
- Add more footers
- Extract version from changelog
- First & Last filters now accept arguments