fix(dist): only distribute necessary files

Author: raphaelstolt

.gitattributes

@@ -1,4 +1,10 @@
-/examples       export-ignore
-.gitattributes  export-ignore
-.gitignore      export-ignore
-phpcs.xml       export-ignore
+# This file was partly modified by the lean package validator (http://git.io/lean-package-validator).
+
+.gitattributes   export-ignore
+.github/ 	     export-ignore
+.gitignore       export-ignore
+examples/        export-ignore
+phpcs.xml        export-ignore
+phpunit.xml.dist export-ignore
+README.md        export-ignore
+tests/           export-ignore