Compatibility with Octopress site.

Don't break urls.
 1. New Route function which generates routes compatible with old blog.
 2. Renamed posts folder to blog.

blogng.cabal

@@ -7,5 +7,7 @@ executable site
   main-is:          site.hs
   build-depends:    base == 4.*
                   , hakyll == 4.9.*
+                  , filepath >= 1.4
+                  , regex-compat
   ghc-options:      -threaded
   default-language: Haskell2010