Fix negative hash values and add destringify function

Added destringify function that accepts a json object. It was also necessary to ensure that calulateHashes returns only positive values.


	var bf0, bfJson, bloem, fs, json, word, words, _i, _j, _len, _len1;
	bloem = require('bloem');
	fs = require('fs');

	bf0 = new bloem.SafeBloem(5, 0.01);

	words = ["monkey", "tree", "beef", "goat", "hamburger"];

	for (_i = 0, _len = words.length; _i < _len; _i++) {
	  word = words[_i];
	  bf0.add(word);
	}

	fs.writeFileSync("./test.json", JSON.stringify(bf0, null, "  "));

	json = require('./test');

	bfJson = bloem.SafeBloem.destringify(json);

	for (_j = 0, _len1 = words.length; _j < _len1; _j++) {
	  word = words[_j];
	  console.log(word, bfJson.has(word), bf0.has(word));
	  console.log(word + "foo", bfJson.has(word + "foo"), bf0.has(word + "foo"));
	}

	console.log(bfJson.filter.bitfield);

	console.log(bf0.filter.bitfield);

monkey true true
monkeyfoo false false
tree true true
treefoo false false
beef true true
beeffoo false false
goat true true
goatfoo false false
hamburger true true
hamburgerfoo false false
{ buffer: \<Buffer e9 4b a5 3f d4 17\> }
{ buffer: \<Buffer e9 4b a5 3f d4 17\> }