Travis conf didn't match schema

- PHP versions need to be strings
- https://docs.travis-ci.com/user/notifications/#configuring-email-notifications

Also: tell editors like PhpStorm how the YAML needs to be formatted.

.editorconfig

@@ -13,3 +13,6 @@ insert_final_newline = true
 
 [composer.json]
 indent_size = 4
+
+[.travis.yml]
+indent_size = 2