[dsch] README: adding npm, build and coverals badges

README.md

@@ -1,4 +1,4 @@
-# Result
+# Result [![Coverage Status](https://coveralls.io/repos/github/DScheglov/ts-result/badge.svg?branch=master&service=github)](https://coveralls.io/github/DScheglov/ts-result?branch=master&service=github) [![npm version](https://img.shields.io/npm/v/ts-result.svg?style=flat-square)](https://www.npmjs.com/package/ts-result) [![npm downloads](https://img.shields.io/npm/dm/ts-result.svg?style=flat-square)](https://www.npmjs.com/package/ts-result) [![GitHub license](https://img.shields.io/badge/license-MIT-blue.svg)](https://github.com/DScheglov/ts-result/blob/master/LICENSE)
 
 Useful type to model success and failure, implemented with focus on type safety,
 developer experience and preserving flat learning curve.