Fix the build

Use the PHPCS `2.9` branch until the external standards are compatible with PHPCS 3.x

.travis.yml

@@ -36,7 +36,8 @@ before_script:
   - export PHPCS_DIR=/tmp/phpcs
   - export SNIFFS_DIR=/tmp/sniffs
   # Install CodeSniffer for WordPress Coding Standards checks.
-  - if [[ "$SNIFF" == "1" ]]; then git clone -b master --depth 1 https://github.com/squizlabs/PHP_CodeSniffer.git $PHPCS_DIR; fi
+  # @TODO Change branch back to master once WPCS + PHPCompatibility are compatible with PHPCS 3.x.
+  - if [[ "$SNIFF" == "1" ]]; then git clone -b 2.9 --depth 1 https://github.com/squizlabs/PHP_CodeSniffer.git $PHPCS_DIR; fi
   # Install WordPress Coding Standards.
   - if [[ "$SNIFF" == "1" ]]; then git clone -b master --depth 1 https://github.com/WordPress-Coding-Standards/WordPress-Coding-Standards.git $SNIFFS_DIR; fi
   # Install PHP Compatibility sniffs.