Updated openstack/openstack
Project: openstack/horizon  3adf22843901e97142a22a60839245eea3366237

Fix build instructions and formatting in README

- Fix manual build command
- Fix formatting of command-line examples, directory names
- Rename 'folder' to 'directory' for consistency
- Update sphinx URL

Partial-bug: #1257725
Change-Id: I078bc5b9c931d4bf4e57c8fe7b335db99cc92c29