ci: drop Travis CI

- end of an era

.travis.yml

@@ -1,13 +0,0 @@
----
-os: linux
-language: ruby
-rvm:
-- 2.7
-- 2.6
-- 2.5
-
-services:
-- docker
-
-script:
-- bundle exec rake ci

CHANGELOG.md

@@ -4,7 +4,7 @@
 
 OTHER:
 
-- start using Github Actions CI for tests in addition to Travis CI
+- start using Github Actions CI for tests and drop Travis CI
 
 ## 3.1.1 (October 3, 2020)
 

README.md

@@ -1,6 +1,6 @@
 # dyndnsd.rb
 
-[![Build Status](https://travis-ci.com/cmur2/dyndnsd.svg?branch=master)](https://travis-ci.com/cmur2/dyndnsd) ![ci](https://github.com/cmur2/dyndnsd/workflows/ci/badge.svg) [![Dependencies](https://badges.depfu.com/badges/4f25da8493f7a29f652ac892fbf9227b/overview.svg)](https://depfu.com/github/cmur2/dyndnsd)
+![ci](https://github.com/cmur2/dyndnsd/workflows/ci/badge.svg) [![Dependencies](https://badges.depfu.com/badges/4f25da8493f7a29f652ac892fbf9227b/overview.svg)](https://depfu.com/github/cmur2/dyndnsd)
 
 A small, lightweight and extensible DynDNS server written with Ruby and Rack.