Remove Travis CI integration (#118)

Travis CI has stopped to support open source projects. Remove the integration.

.travis.yml

@@ -1,27 +0,0 @@
-dist: focal
-
-language: cpp
-
-os: linux
-arch:
-  - amd64
-  - ppc64le
-
-compiler:
-  - gcc
-  - clang
-
-addons:
-  apt:
-    sources:
-    - ubuntu-toolchain-r-test
-    - llvm-toolchain-precise-3.7
-
-sudo: false
-
-before_script:
-  - mkdir debug
-  - cd debug
-  - cmake -DCMAKE_BUILD_TYPE=Debug -DCHARLS_PEDANTIC_WARNINGS=On -DCHARLS_TREAT_WARNING_AS_ERROR=On ..
-
-script: make

README.md

@@ -5,7 +5,6 @@
 
 [![License](https://img.shields.io/badge/License-BSD%203--Clause-blue.svg)](https://raw.githubusercontent.com/team-charls/charls/master/LICENSE.md)
 [![Build status](https://ci.appveyor.com/api/projects/status/yq0naf3v2m8nfa8r/branch/master?svg=true)](https://ci.appveyor.com/project/vbaderks/charls/branch/master)
-[![Build Status](https://travis-ci.org/team-charls/charls.svg?branch=master)](https://travis-ci.org/team-charls/charls)
 [![Build Status](https://dev.azure.com/team-charls/charls/_apis/build/status/team-charls.charls?branchName=master)](https://dev.azure.com/team-charls/charls/_build/latest?definitionId=2&branchName=master)
 [![Vcpkg package](https://repology.org/badge/version-for-repo/vcpkg/charls.svg)](https://repology.org/metapackage/charls)