Downgrade metalsmith to 1.7.0, restoring node.js 0.10 and 0.12 support

Author: papandreou

package.json

@@ -27,7 +27,7 @@
     "ejs": "2.5.6",
     "glob": "7.1.1",
     "lodash": "4.17.4",
-    "metalsmith": "2.3.0",
+    "metalsmith": "1.7.0",
     "metalsmith-autoprefixer": "1.1.1",
     "metalsmith-collections": "0.9.0",
     "metalsmith-less": "2.0.0",