Add Badge [Codecov, Travis]

Author: kimtaesu

README.md

@@ -4,6 +4,11 @@
    <a href="https://developer.apple.com/swift/">
       <img src="https://img.shields.io/badge/Swift-5.0-orange.svg?style=flat" alt="Swift 5.0">
    </a>
+   <a href="https://travis-ci.com/SwiftAlgorithmClub/AGString">
+      <img src="https://travis-ci.com/SwiftAlgorithmClub/AGString.svg?branch=master" alt="SPM">   </a>
+   <a href="https://codecov.io/gh/SwiftAlgorithmClub/AGString">
+      <img src="https://codecov.io/gh/SwiftAlgorithmClub/AGString/branch/develop/graph/badge.svg" alt="SPM">
+   </a>
    <a href="http://cocoapods.org/pods/AGString">
       <img src="https://img.shields.io/cocoapods/v/AGString.svg?style=flat" alt="Version">
    </a>