Update build and preview scripts

This MR updates the build scripts in this repo:

• jekyll-build.sh is now the deploy script used to build the production site on the server
• jekyll-preview.sh creates a local preview of the website locally, rebuilding every time a file changes through the --watch flag
• scripts/gen_member_list.sh now sorts the member list and creates the _members dir if it doesn't exist
• clean up the repo and add the preview script to the list of ignored files in _config.yml