Update .gitignore (#2366)

.gitignore

@@ -1,16 +1,29 @@
-*.gem
+# Vim
+*~
+*.sw[p_]
+
+# Sublime Text
 *.sublime-project
 *.sublime-workspace
+
+# Ruby Gem
+*.gem
 .bundle
+Gemfile.lock
+vendor/bundle
+
+# Node.js and NPM
+node_modules
+npm-debug.log*
+package-lock.json
+codekit-config.json
+
+# macOS
 .DS_Store
+
+# Jekyll generated files
 .jekyll-cache
 .jekyll-metadata
 .sass-cache
 _asset_bundler_cache
 _site
-codekit-config.json
-example/_site
-Gemfile.lock
-node_modules
-npm-debug.log*
-vendor/bundle