README uses new Filter builder. Resolves #54

README.rst

@@ -90,12 +90,15 @@ Query or scan by column values:
     email = 'foo@bar.com'
     yesterday = arrow.now().replace(days=-1)
 
-    account = engine.query(Account.by_email)\
-                   .key(Account.email == email).first()
-    tweets = engine.query(Tweet)\
-                   .key(Tweet.account == account.id)
+    acct_query = engine.query(Account.by_email)
+    acct_query.key = Account.email == email
+    account = acct_query.first()
 
-    for tweet in tweets.filter(Tweet.date >= yesterday):
+    tweet_query = engine.query(Tweet)
+    tweet_query.key = Tweet.account == account.id
+    tweet_query.filter = Tweet.date >= yesterday
+
+    for tweet in tweet_query.build():
         print(tweet.content)