Updates to usage.md (#1970)
Updates to usage.md (#1970)

- Updated file tree with relevant additions, filename changes and
alphabetized
- Mention that browserconfig.xml is relevant for Edge (as well as IE11)
- Remove very old link with favicon.psd. It is deprecated and doesn't
have any of the recent iPhones app sizes.
roblarsen/html5-boilerplate,rprouse/html5-boilerplate,roblarsen/html5-boilerplate,JohnnyWalkerDesign/html5-boilerplate,byog/html5-boilerplate,JohnnyWalkerDesign/html5-boilerplate,rprouse/html5-boilerplate,Upmacis-Andrejs/12guru_Front-end,h5bp/html5-boilerplate,h5bp/html5-boilerplate,Upmacis-Andrejs/12guru_Front-end,byog/html5-boilerplate