ci(macos): fix macos php installation (#257)

Author: felixfbecker

.travis.yml

@@ -46,11 +46,11 @@ jobs:
       before_install:
         # Fix ruby error https://github.com/Homebrew/brew/issues/3299
         - brew update
-        - brew tap homebrew/homebrew-php
-        - brew install php71
-        - brew install homebrew/php/php71-xdebug
-        - mkdir -p /usr/local/etc/php/7.1/conf.d
-        - cp travis-php.ini /usr/local/etc/php/7.1/conf.d/
+        - brew install php@7.0
+        - brew link --force --overwrite php@7.0
+        - pecl install xdebug-$XDEBUG_VERSION
+        - mkdir -p /usr/local/etc/php/7.0/conf.d
+        - cp travis-php.ini /usr/local/etc/php/7.0/conf.d/
         - git clone --depth 1 https://github.com/creationix/nvm.git ./.nvm
         - source ./.nvm/nvm.sh
         - nvm install $NODE_VERSION