Make 'numberOfRecords' null when 'completeListSize' not given.

If the server doesn't return 'completeListSize', it's better to make
it clear that we have no clue how many records we will get.

src/Records.php

@@ -34,8 +34,10 @@ class Records extends EventEmitter implements \Iterator {
 	private $resumptionToken;
 	private $initialResumptionToken;
 
-    /** @var int Total number of records in the result set */
-    public $numberOfRecords;
+	/** @var int Total number of records in the result set. Only defined if the
+	    server returns 'completeListSize', which is optional. Even if defined, the
+	    value may still be only an estimate. */
+	public $numberOfRecords = null;
 
 	private $data = array();
 
@@ -135,12 +137,11 @@ private function fetchMore()
 
 		$this->data = $this->lastResponse->records;
 
-		if (isset($this->lastResponse->numberOfRecords) && !is_null($this->lastResponse->numberOfRecords)) {
+		if (!is_null($this->lastResponse->numberOfRecords)) {
 			$this->numberOfRecords = $this->lastResponse->numberOfRecords;
-			$this->position = $this->lastResponse->cursor + 1;
-
-		} else if (!isset($this->numberOfRecords)) {
-			$this->numberOfRecords = count($this->lastResponse->records);
+			if (!is_null($this->lastResponse->cursor)) {
+				$this->position = $this->lastResponse->cursor + 1;
+			}
 		}
 
 		if (isset($this->lastResponse->resumptionToken)) {

tests/RecordsTest.php

@@ -67,7 +67,7 @@ public function testBasicIteration()
 		$client = new Client($uri, null, $http);
 		$records = new Records($args['from'], $args['until'], $args['set'], $client);
 
-		$this->assertEquals(8, $records->numberOfRecords);
+		$this->assertNull($records->numberOfRecords);
 		$records->rewind();
 
 		$this->assertEquals(1, $records->key());