Exclude files in production (#193)

* Exclude files in production

With this .gitattributes files, unwanted files/folders in production are not installed.
By default, I propose you to keep only the library and template files.
Feel free to ask if you have any reason to keep some of them.

* Update .gitattributes

As per @dunglas comments

Author: Spomky

.gitattributes

@@ -0,0 +1,11 @@
+data export-ignore
+tests export-ignore
+.editorconfig export-ignore
+.php_cs.dist export-ignore
+.travis.yml export-ignore
+box.json.dist export-ignore
+composer.lock export-ignore
+CONTRIBUTING.md export-ignore
+phpstan.neon export-ignore
+phpunit.xml.dist export-ignore
+scoper.inc.php export-ignore