update badges

Author: petercorke

README.md

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 [![Build Status](https://travis-ci.com/petercorke/spatial-math.svg?branch=master)](https://travis-ci.com/petercorke/spatial-math)
 ![Coverage](https://codecov.io/gh/petercorke/spatial-math/branch/master/graph/badge.svg)
 [![License: MIT](https://img.shields.io/badge/License-MIT-blue.svg)](https://opensource.org/licenses/MIT)
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 # Spatial Math Toolbox for MATLAB®