Updated guzzle version in composer + miner update in tests

composer.json

@@ -10,7 +10,7 @@
         }
     ],
     "require": {
-        "guzzlehttp/guzzle": "~6.0",
+        "guzzlehttp/guzzle": "~7.0",
         "PHP": "^7.1",
         "kornrunner/keccak": "~1.0",
         "phpseclib/phpseclib": "~2.0.11",

test/unit/PersonalApiTest.php

@@ -175,7 +175,7 @@ class PersonalApiTest extends TestCase
         $this->web3->eth->sendTransaction([
             'from' => $this->coinbase,
             'to' => $this->newAccount,
-            'value' => '0xfffffffff',
+            'value' => '0xfffffffffffff',
         ], function ($err, $transaction) {
             if ($err !== null) {
                 return $this->fail($err->getMessage());