Add build status and licence badge

Author: ztombol

README.md

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 # bats-assert
 
+[![GitHub license](https://img.shields.io/badge/license-CC0-blue.svg)](https://raw.githubusercontent.com/ztombol/bats-assert/master/LICENSE)
+[![Build Status](https://travis-ci.org/ztombol/bats-assert.svg?branch=master)](https://travis-ci.org/ztombol/bats-assert)
+
 `bats-assert` is a helper library providing common assertions for
 [Bats][bats].