v0.6.0

• Optimised assets with sprockets, and new asset workflow
• README updates
• Make URLs in plain text clickable
• Persist separator sizing
• Make catchmail more like actual sendmail
• Differentiate exit codes
• Make sure IO is synchronous when running in foreground
• Fix line endings on SMTP receipt
• Favicon message count
• Remove broken Fractal analysis
• Remove growl
• Some acceptance spec
• Make sure secure websockets work
• Dockerfile