Get all records implementation (#21)

* Implementation of all() and updated README.md

* fixed styling

* another fix

Author: albalooshi

README.md

@@ -60,11 +60,21 @@ If you need to support multiple tables, add them to the tables config in the con
 use Airtable;
 ```
 
-#### Get all records from that table.
+#### Get records from that table
+- This will only return the first 100 records due to Airtable page size limiation
+
 ``` php
 Airtable::table('tasks')->get();
 ```
 
+#### Get all records from that table.
+- This will get all records by sending multiple requests until all record are fetched.
+- Optional Parameter which is the delay between requests in microseconds as API is limited to 5 requests per second per base, defaults to 0.2 second.
+``` php
+Airtable::table('tasks')->all();
+Airtable::table('tasks')->all(500000); // 0.5 seconds
+```
+
 #### Get one record from the default table.
 ``` php
 Airtable::find('id_string');

src/Airtable.php

@@ -41,9 +41,13 @@ public function get()
         return $this->toCollection($this->api->get());
     }
 
-    public function all()
+    // There is delay between requests to avoid 429 error
+    // 1000000 = 1 second
+    // "The API is limited to 5 requests per second per base. If you exceed this rate, you will receive a 429 status code
+    //  and will need to wait 30 seconds before subsequent requests will succeed."
+    public function all($delayBetweenRequestsInMicroseconds = 200000)
     {
-        return $this->toCollection($this->api->getAllPages());
+        return $this->toCollection($this->api->getAllPages($delayBetweenRequestsInMicroseconds));
     }
 
     public function table($table)

src/Api/AirtableApiClient.php

@@ -68,20 +68,39 @@ public function get(?string $id = null)
         return $this->decodeResponse($this->client->get($url));
     }
 
-    public function getAllPages()
+    public function getAllPages($delayBetweenRequestsInMicroseconds)
     {
         $url = $this->getEndpointUrl();
 
-        $response = $this->client->get($url, [
-            'query' => [
-                'pageSize' => $this->pageSize,
-                'maxRecords' => $this->maxRecords,
-            ],
-        ]);
+        $records = [];
+        $offset = false;
+
+        do {
+            $query = []; // page sizes defaults to 100
+
+            if ($offset) {
+                $query['offset'] = $offset;
+            }
+
+            $response = $this->client->get($url, [
+                'query' => $query,
+            ]);
+
+            $response = $this->decodeResponse($response);
+
+            if (isset($response['records'])) {
+                $records = array_merge($response['records'], $records);
+            }
 
-        //TODO: loop through offset to get more than one page when more than 100 records exist
+            if (isset($response['offset'])) {
+                $offset = $response['offset'];
+                usleep($delayBetweenRequestsInMicroseconds);
+            } else {
+                $offset = false;
+            }
+        } while ($offset);
 
-        return $this->decodeResponse($response);
+        return collect($records);
     }
 
     public function post($contents = null)