`travisjs badge` is broken @ node v6

```
$ node -v
v6.0.0

$ travisjs badge
(node:20670) fs: re-evaluating native module sources is not supported. If you are using the graceful-fs module, please update it to a more recent version.
[](https://travis-ci.org/textlint/textlint)
```

[graceful-fs](https://github.com/isaacs/node-graceful-fs) show warning message and break following use-case.

```
$ travisjs badge | pbcopy
```

Reproduce `travisjs badge` under Node v6 and compare its output when piped to `pbcopy`. Start at the `travisjs badge` command entry point and inspect how the `graceful-fs` warning reaches stdout. Done means the badge output can be piped cleanly without the warning breaking the generated Markdown.

Written by the indexing model from the issue text.