Update .gitattributes file

Updates the `.gitattributes` to account for the latest changes in the
repo.

 - `.travis.yml` is no longer used: removed
 - PHP CS files: updated

This reduces the library zip file size form 12.61 KiB to 9.21 KiB.
It's not much, but it's a 26% size reduction, and assuming this library
gets ~400K installs a day, that's about 1.2 GiB of bandwidth saved per
day :)

Author: Ayesh

.gitattributes

@@ -1,9 +1,9 @@
-/.github         export-ignore
-/tests           export-ignore
-/.gitattributes  export-ignore
-/.gitignore      export-ignore
-/.php_cs.dist    export-ignore
-/.travis.yml     export-ignore
-/build.xml       export-ignore
-/phive.xml       export-ignore
-/phpunit.xml     export-ignore
+/.gitattributes         export-ignore
+/.github                export-ignore
+/.gitignore             export-ignore
+/.php-cs-fixer.dist.php export-ignore
+/build.xml              export-ignore
+/phive.xml              export-ignore
+/phpunit.xml            export-ignore
+/tests                  export-ignore
+/tools/php-cs-fixer.d   export-ignore