A modest version bump for some dependencies

Author: rowan-m

.travis.yml

@@ -3,11 +3,12 @@ language: php
 sudo: false
 
 php:
-  - 5.3
-  - 5.4
-  - 5.5
-  - 5.6
+  - '5.5'
+  - '5.6'
+  - '7.0'
+  - '7.1'
   - hhvm
+  - nightly
 
 before_script:
   - composer install

composer.json

@@ -10,10 +10,10 @@
         "source": "https://github.com/google/recaptcha"
     },
     "require": {
-        "php": ">=5.3.2"
+        "php": ">=5.5"
     },
     "require-dev": {
-        "phpunit/phpunit": "4.5.*"
+        "phpunit/phpunit": "^4.8"
     },
     "autoload": {
         "psr-4": {