1. Note: All base files are now located under the vendor directory.
   1. These need to be added retaining the directory structure to app/design/frontend/Webtomarket/ (Make the vendor name Webtomarket for consistency).
   2. Always check the Luma theme for files first.
2. Basic theme set up: http://devdocs.magento.com/guides/v2.0/frontend-dev-guide/themes/theme-create.html
3. In vendor/magento/theme-frontend-blank/Magento_Theme/layout
   1. Grab the default_head_blocks.xml file and copy it into your app/design/frontend/Webtomarket/Matrix/Magento_Theme/layout folder
      1. In default_head_blocks.xml, add <css src="css/yoursheetname.css" after="-"/>Update footer
      2. Copy the default.xml file from /vendor/magento/theme-frontend-luma/Magento_Theme/layout/default.xml to app/design/frontend/Webtomarket/Matrix/Magento_Theme/layout folder
   2. Make a new subdirectory in your theme app/design/frontend/Webtomarket/Matrix/Magento_Theme/web/css
      1. Add your custom css file(s) here

A clean bootstrap.css file is attached that should be free of most rules that could conflict with the Luma theme.