remove some duplicated code

lib/deduplicate.js

@@ -1,11 +0,0 @@
-// remove duplicate elements in an array
-module.exports = function (O) {
-    // make a copy of the original array
-    var A = O.slice();
-    for (var i = 0; i < A.length; i++) {
-        for (var j = i + 1; j < A.length; j++) {
-            if (A[i] === A[j]) { A.splice(j--, 1); }
-        }
-    }
-    return A;
-};

lib/hk-util.js

@@ -3,7 +3,7 @@
 var HK = module.exports;
 
 const nThen = require('nthen');
-const Once = require("./once");
+const Util = require("./common-util");
 const Meta = require("./metadata");
 const Nacl = require('tweetnacl/nacl-fast');
 
@@ -182,7 +182,7 @@ const computeIndex = function (Env, channelName, cb) {
 
     const ref = {};
 
-    const CB = Once(cb);
+    const CB = Util.once(cb);
 
     const offsetByHash = {};
     let size = 0;

lib/metadata.js

@@ -1,6 +1,6 @@
 var Meta = module.exports;
 
-var deduplicate = require("./deduplicate");
+var deduplicate = require("./common-util").deduplicateString;
 
 /*  Metadata fields:
 

lib/once.js

@@ -1,7 +0,0 @@
-module.exports = function (f, g) {
-    return function () {
-        if (!f) { return; }
-        f.apply(this, Array.prototype.slice.call(arguments));
-        f = g;
-    };
-};