Update braintre_php to v3.30.0 (braintree#38)

* Update braintre_php to v3.30.0

closes braintree#37

* Update the version of PHPUnit used

* Use PHP 5.6 as it is currently oldest PHP version supported

Author: crookedneighbor

.travis.yml

@@ -1,6 +1,7 @@
 language: php
 php:
-  - '5.4'
+  - '5.6'
+  - '7.2'
 before_script: composer install
 script: vendor/bin/phpunit
 notifications:

composer.json

@@ -1,11 +1,11 @@
 {
   "require" : {
-    "braintree/braintree_php" : "3.6.1",
+    "braintree/braintree_php" : "3.30.0",
     "php": ">=5.2.1",
     "vlucas/phpdotenv": "2.1.0"
   },
   "require-dev": {
-    "phpunit/phpunit": "3.7.*",
+    "phpunit/phpunit": "5.*",
     "ext-curl": "*"
   }
 }