Release of signac version 0.8.4

This release improves search capabilities and largely simplifies searching on the command line.

Highlights of version 0.8.4:

• logical, arithmetic, and other search operators for collections and projects
• simplified query formulation on the command line
• the signac find --show command provides a brief overview of state points and job document content directly on the command line

Details may be found – as usual – in the changelog.