Add Symfony Coding Standard & PHP CodeSniffer to require-dev #21

- Add `escapestudios/symfony2-coding-standard` to require-dev
- Add `squizlabs/php_codesniffer` to require-dev
- Add `phpcs.xml` as a default PHP CodeSniffer configuration

composer.json

@@ -29,7 +29,9 @@
         "phpunit/php-code-coverage": "~6.0"
     },
     "require-dev": {
-        "bossa/phpspec2-expect": "^3.0"
+        "bossa/phpspec2-expect": "^3.0",
+        "escapestudios/symfony2-coding-standard": "^3.1",
+        "squizlabs/php_codesniffer": "^3.2"
     },
     "suggest": {
         "ext-xdebug": "Install Xdebug to generate phpspec code coverage if you are not using phpdbg"

phpcs.xml

@@ -0,0 +1,20 @@
+<?xml version="1.0"?>
+<!-- leanphp/common-dev phpcs.xml example config -->
+<ruleset name="LeanPHP Coding Standard">
+    <description>LeanPHP Coding Standard</description>
+
+    <!-- directories and files to scan -->
+    <file>src</file>
+
+    <!-- directories and files to exclude -->
+    <exclude-pattern>test</exclude-pattern>
+    <exclude-pattern>tests</exclude-pattern>
+    <exclude-pattern>*Spec.php</exclude-pattern>
+
+    <!-- uncomment for a summary instead of detailed report -->
+    <!--<arg name="report" value="summary"/>-->
+    <arg value="p"/>>
+
+    <!-- Use Symfony2 Coding Standard -->
+    <rule ref="vendor/escapestudios/symfony2-coding-standard/Symfony"/>
+</ruleset>