TryGhost/Ghost — pull request #2923 by gcochard (2014-06-09 18:44:36+00:00)
Title: Adding support for disabling or setting custom x-powered-by header.

- If config property customPoweredBy is false, disables the x-powered-by header.
- If property customPoweredBy is true, sets the value to 'Ghost'.
- If property is undefied, does nothing and lets express set the header.
- If property is any other value, sets the value to config value.