Tweak css-prefix scripts.

* rename `css-prefix` scripts to `css-postcss`
* don't run postcss for `dist/css/*.min.css` files

Author: XhmikosR

package.json

@@ -18,15 +18,15 @@
   ],
   "scripts": {
     "bundlesize": "bundlesize",
-    "css": "npm-run-all --parallel css-lint* css-compile* --sequential css-prefix* css-minify*",
-    "css-main": "npm-run-all --parallel css-lint css-compile --sequential css-prefix css-minify",
-    "css-docs": "npm-run-all --parallel css-lint-docs css-compile-docs --sequential css-prefix-docs css-minify-docs",
+    "css": "npm-run-all --parallel css-lint* css-compile* --sequential css-postcss* css-minify*",
+    "css-main": "npm-run-all --parallel css-lint css-compile --sequential css-postcss css-minify",
+    "css-docs": "npm-run-all --parallel css-lint-docs css-compile-docs --sequential css-postcss-docs css-minify-docs",
     "css-compile": "node-sass --output-style expanded --source-map true --source-map-contents true --precision 6 scss/bootstrap.scss dist/css/bootstrap.css && node-sass --output-style expanded --source-map true --source-map-contents true --precision 6 scss/bootstrap-grid.scss dist/css/bootstrap-grid.css && node-sass --output-style expanded --source-map true --source-map-contents true --precision 6 scss/bootstrap-reboot.scss dist/css/bootstrap-reboot.css",
     "css-compile-docs": "node-sass --output-style expanded --source-map true --source-map-contents true --precision 6 assets/scss/docs.scss assets/css/docs.min.css",
     "css-lint": "stylelint --config build/.stylelintrc --syntax scss \"scss/**/*.scss\"",
     "css-lint-docs": "stylelint --config build/.stylelintrc --syntax scss \"assets/scss/*.scss\" && stylelint --config docs/4.0/examples/.stylelintrc \"docs/**/*.css\"",
-    "css-prefix": "postcss --config build/postcss.config.js --replace \"dist/css/*.css\"",
-    "css-prefix-docs": "postcss --config build/postcss.config.js --replace \"assets/css/docs.min.css\" \"docs/**/*.css\"",
+    "css-postcss": "postcss --config build/postcss.config.js --replace \"dist/css/*.css\" \"!dist/css/*.min.css\"",
+    "css-postcss-docs": "postcss --config build/postcss.config.js --replace \"assets/css/docs.min.css\" \"docs/**/*.css\"",
     "css-minify": "cleancss --level 1 --source-map --source-map-inline-sources --output dist/css/bootstrap.min.css dist/css/bootstrap.css && cleancss --level 1 --source-map --source-map-inline-sources --output dist/css/bootstrap-grid.min.css dist/css/bootstrap-grid.css && cleancss --level 1 --source-map --source-map-inline-sources --output dist/css/bootstrap-reboot.min.css dist/css/bootstrap-reboot.css",
     "css-minify-docs": "cleancss --level 1 --source-map --source-map-inline-sources --output assets/css/docs.min.css assets/css/docs.min.css",
     "js": "npm-run-all js-lint* js-compile js-minify",