Fix Travis CI badge.
Fix Travis CI badge.

I don't know if it's that GitHub's image caching doesn't know how
to handle redirects or what, but this doesn't seem to show up
even though it's a valid URL.

Signed-off-by: Julian C. Dunn <jdunn@chef.io>

Pull request: #914
Approved by: reset

nathenharvey/habitat,rsertelon/habitat,georgemarshall/habitat,georgemarshall/habitat,georgemarshall/habitat,rsertelon/habitat,nathenharvey/habitat,habitat-sh/habitat,nathenharvey/habitat,rsertelon/habitat,nathenharvey/habitat,habitat-sh/habitat,habitat-sh/habitat,georgemarshall/habitat,georgemarshall/habitat,rsertelon/habitat,habitat-sh/habitat,georgemarshall/habitat,rsertelon/habitat,rsertelon/habitat,habitat-sh/habitat,nathenharvey/habitat,nathenharvey/habitat,habitat-sh/habitat,habitat-sh/habitat,georgemarshall/habitat,habitat-sh/habitat,rsertelon/habitat,georgemarshall/habitat