updated README for badge details

Author: Pramod-Devireddy

.travis.yml

@@ -1,13 +1,17 @@
 language: go
 
 go:
-  - 1.2
-  - 1.3
+  - 1.12.x
+  - 1.13.x
   - 1.14.x
   - 1.15.x
   - "1.16.3"
 
 env:
   - GOARCH: amd64
+  
 script:
-  - go test -v
+  - go test -race -coverprofile=coverage.txt -covermode=atomic
+
+after_success:
+  - bash <(curl -s https://codecov.io/bash)

README.md

@@ -2,7 +2,22 @@
     <h1 align="center"> Go Mathematical Expression Toolkit</h1>
 </p>
 
-[![Go Report Card](https://goreportcard.com/badge/github.com/Pramod-Devireddy/go-exprtk)](https://goreportcard.com/report/github.com/Pramod-Devireddy/go-exprtk)
+<p align="center">
+  <a href="https://godoc.org/github.com/Pramod-Devireddy/go-exprtk">
+  	<img src="https://godoc.org/github.com/Pramod-Devireddy/go-exprtk?status.svg" alt="Go Doc Reference">
+  </a>
+  <a href="https://travis-ci.com/Pramod-Devireddy/go-exprtk">
+  <img src="https://www.travis-ci.com/Pramod-Devireddy/go-exprtk.svg?branch=main" alt="Build Status">
+  </a>
+  <a href="https://codecov.io/gh/Pramod-Devireddy/go-exprtk">
+  	<img src="https://codecov.io/gh/Pramod-Devireddy/go-exprtk/branch/main/graph/badge.svg?token=9pNExL9yZt"/>
+  </a>
+  <a href="https://goreportcard.com/report/github.com/Pramod-Devireddy/go-exprtk">
+  	<img src="https://goreportcard.com/badge/github.com/Pramod-Devireddy/go-exprtk" alt="Go Report Card">
+  </a>
+</p>
+
+
 
 The Go Expression Toolkit (Go-ExprTk) is a wrapper library based on C++ Mathematical Expression Toolkit Library ([ExprTk](http://www.partow.net/programming/exprtk/)).