Remove travis.yml and appveyor.yml (#47)

* Remove travis.yml and appveyor.yml

* Remove travis and appveyor badge from readme.md

Author: jangko

.appveyor.yml

@@ -1,7 +1,5 @@
 # nimPDF
 
-[![Build Status (Travis)](https://img.shields.io/travis/jangko/nimpdf/master.svg?label=Linux%20/%20macOS "Linux/macOS build status (Travis)")](https://travis-ci.org/jangko/nimpdf)
-[![Windows build status (Appveyor)](https://img.shields.io/appveyor/ci/jangko/nimpdf/master.svg?label=Windows "Windows build status (Appveyor)")](https://ci.appveyor.com/project/jangko/nimpdf)
 ![nimble](https://img.shields.io/badge/available%20on-nimble-yellow.svg?style=flat-square)
 ![license](https://img.shields.io/github/license/citycide/cascade.svg?style=flat-square)
 ![Github action](https://github.com/jangko/nimPDF/workflows/nimPDF%20CI/badge.svg)