Fixes #278 filter files by extension

example/index.html

@@ -18,6 +18,9 @@
       },
       "2015-02-16-this-is-a-toml-frontmatter-post.md": {
         content: "+++\ntitle = \"This is a TOML front matter post\"\nimage = \"/nf-logo.png\"\n\"date\" = \"2015-02-16T00:00:00.000Z\"\n+++\n\n# I Am a Title in Markdown\n\nHello, world\n\n* One Thing\n* Another Thing\n* A Third Thing\n"
+      },
+      "2015-02-14-this-is-a-post-with-a-different-extension.other": {
+        content: "---\ntitle: This post should not appear because the extension is different\nimage: /nf-logo.png\ndate: 2015-02-14T00:00:00.000Z\n---\n\n# I Am a Title in Markdown\n\nHello, world\n\n* One Thing\n* Another Thing\n* A Third Thing\n"
       }
     },
     _faqs: {