Setup PHP CS fixer

- Add PHP CS Fixer as a dev dependencies.
- Add PHP CS Fixer cache file to gitignore/gitattributes
- Add custom code style config
- Update TravisCI config to check code style

.gitattributes

@@ -1,11 +1,11 @@
-# Ignore all test and documentation for archive
+# Ignore all test, documentation and dot files for archive
 /tests              export-ignore
 /.editorconfig      export-ignore
 /.gitattributes     export-ignore
 /.gitignore         export-ignore
+/.php_cs.dist       export-ignore
 /.scrutinizer.yml   export-ignore
 /.travis.yml        export-ignore
-/composer.lock      export-ignore
 /CONTRIBUTING.md    export-ignore
 /logo.png           export-ignore
 /phpunit.xml        export-ignore