Minor changes to comments in README and configuration settings.
Allow empty output buffers to be hidden.
Start progress bar on initiating window.

This is in case we have a long-running empty command -- we'll be sat there wondering whether anything is actually happening!
Minor change to README.
Describe configuration settings for 'empty output' message in README.
Merge branch 'feature/11-no-output' into develop
Bump version number.
Update changelog.
Merge branch 'release/0.5.0' into develop