Exclude unnecessary files from release archive exports

Author: colinodell

.gitattributes

@@ -0,0 +1,9 @@
+# Path-based git attributes
+# https://www.kernel.org/pub/software/scm/git/docs/gitattributes.html
+
+# Ignore all test and documentation with "export-ignore".
+/.gitattributes       export-ignore
+/.gitignore           export-ignore
+/.travis.yml          export-ignore
+/phpunit.xml.dist     export-ignore
+/tests                export-ignore