title: stackexchange redis hashscan return all fields in one time
body: <p>I'm using stackexchange.redis SDK in C#, and wish to scan my hash set.
  I expected the SDK executed as redis client(when I execute "hscan myKey 0", it will return several key-value pairs, and an cursor which I'll use for the next scan). But when I use stackexchange.redis SDK to implement the "hashscan" method as following:</p>
  
  <pre><code>redisCache.HashScan(myKey, pageSize:10, cursor: 0)
  </code></pre>
  
  <p>It will return all the fields in "myKey", there are 2,000 key-value pairs in it.
  How can I let it just return several results at one time? </p>
  
  <p>Cause In the future, there will be millions of fields in "myKey", if they all return at one time, it'll cost lots of memory, and will it block the online service? Cause redis is single thread application.</p>
  
  <p>Thanks!</p>