Redo and add more documentation to gh-pages.

docs/plugins/wintersmith-makerelative.coffee

@@ -0,0 +1,15 @@
+module.exports = (env, callback) ->
+  count = (string, substr) ->
+    num = pos = 0
+    return 1/0 unless substr.length
+    num++ while pos = 1 + string.indexOf(substr, pos)
+    num
+
+  env.helpers.makeRelative = (source, dest) ->
+    return dest unless dest.indexOf("/") == 0
+    depth = count(source, '/') # 1 being /
+    ret = ""
+    ret += "../" while depth = depth - 1
+    ret + dest.substr(1)
+
+  callback()