Remove unnecessary files in release tarball
Prior to this patch, we would find '.gitignore', '.travisCI.yml' in
the release tarball.
This patch adds a few entries in .gitattributes to specify files that
should never end up in a distribution tarball.
* text=auto
/tests/inputs/* text eol=lf
+
+.gitattributes export-ignore
+.gitignore export-ignore
+.github export-ignore
+.editorconfig export-ignore
+.travis.yml export-ignore
