Added getID to PublicKey

- Tests in BloomFilter in [bitcoin core](https://github.com/bitcoin/bitcoin/blob/master/src/test/bloom_tests.cpp#L85) use the CPubKey.GetID as input into the BloomFilter
- The hash is calculated when generating an Address however the hash itself is not currently available

lib/publickey.js

@@ -3,6 +3,7 @@
 var Address = require('./address');
 var BN = require('./crypto/bn');
 var Point = require('./crypto/point');
+var Hash = require('./crypto/hash');
 var JSUtil = require('./util/js');
 var Network = require('./networks');
 var _ = require('lodash');
@@ -384,6 +385,15 @@ PublicKey.prototype.toBuffer = PublicKey.prototype.toDER = function() {
   }
 };
 
+/*
+ * Will return a sha256 + ripemd160 hash of the serialized public key
+ * @see https://github.com/bitcoin/bitcoin/blob/master/src/pubkey.h#L141
+ * @returns {Buffer}
+ */
+PublicKey.prototype.getID = function getID() {
+  return Hash.sha256ripemd160(this.toBuffer())
+}
+
 /**
  * Will return an address for the public key
  *

test/publickey.js

@@ -8,6 +8,7 @@ var Point = bitcore.crypto.Point;
 var BN = bitcore.crypto.BN;
 var PublicKey = bitcore.PublicKey;
 var PrivateKey = bitcore.PrivateKey;
+var Address = bitcore.Address;
 var Networks = bitcore.Networks;
 
 /* jshint maxlen: 200 */
@@ -340,6 +341,25 @@ describe('PublicKey', function() {
 
   });
 
+  describe('hashes', function() {
+
+    // wif private key, address
+    // see: https://github.com/bitcoin/bitcoin/blob/master/src/test/key_tests.cpp#L20
+    var data = [
+      ['5HxWvvfubhXpYYpS3tJkw6fq9jE9j18THftkZjHHfmFiWtmAbrj', '1QFqqMUD55ZV3PJEJZtaKCsQmjLT6JkjvJ'],
+      ['5KC4ejrDjv152FGwP386VD1i2NYc5KkfSMyv1nGy1VGDxGHqVY3', '1F5y5E5FMc5YzdJtB9hLaUe43GDxEKXENJ'],
+      ['Kwr371tjA9u2rFSMZjTNun2PXXP3WPZu2afRHTcta6KxEUdm1vEw', '1NoJrossxPBKfCHuJXT4HadJrXRE9Fxiqs'],
+      ['L3Hq7a8FEQwJkW1M2GNKDW28546Vp5miewcCzSqUD9kCAXrJdS3g', '1CRj2HyM1CXWzHAXLQtiGLyggNT9WQqsDs']
+    ];
+    
+    data.forEach(function(d){
+      var publicKey = PrivateKey.fromWIF(d[0]).toPublicKey();
+      var address = Address.fromString(d[1]);
+      address.hashBuffer.should.deep.equal(publicKey.getID());
+    });
+    
+  });
+
   describe('#toString', function() {
 
     it('should print this known public key', function() {