Add docs badge to README
Add docs badge to README

Add a docs badge to the README to show off inline-documentation to
potential contributors.

The badge links to Inch CI, a project that tries to raise the visibility
of inline-docs to encourage aspiring Rubyists to document their code.

Status page is available at http://inch-ci.org/github/causes/scss-lint/

Change-Id: I03485dc4ef8363f0d71fe55f930a0df631fed040
Reviewed-on: http://gerrit.causes.com/40374
Tested-by: jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@causes.com>
Reviewed-by: Shane da Silva <67fb7bfe39f841b16a1f86d3928acc568d12c716@brigade.com>

artemartemov/scss-lint-hdm