Switch from Travis to GitHub Actions (#59)

The Travis builds are taking a while, whereas on GitHub
Actions builds are super fast, with minimal configuration.

Author: parndt

.github/workflows/main.yml

@@ -0,0 +1,27 @@
+name: CI
+
+on: [ push ]
+
+jobs:
+  test:
+    strategy:
+      matrix:
+        ruby: [ 2.5, 2.6, 2.7, jruby, truffleruby-head ]
+      fail-fast: false
+      max-parallel: 10
+    runs-on: ubuntu-latest
+
+    env:
+      BUNDLE_JOBS: 4
+      BUNDLE_PATH: vendor/bundle
+      CI: true
+
+    name: ${{ matrix.ruby }}
+    steps:
+      - uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true
+          ruby-version: ${{ matrix.ruby }}
+      - uses: actions/checkout@v2
+      - run: bundle install --path vendor/bundle
+      - run: bundle exec rake

.travis.yml

@@ -1,7 +1,6 @@
 # Babosa
 
-[![Build Status](https://api.travis-ci.com/norman/babosa.svg?branch=master)](https://travis-ci.com/norman/babosa)
-
+[![Build Status](https://github.com/norman/babosa/actions/workflows/main.yml/badge.svg)](https://github.com/norman/babosa/actions)
 
 Babosa is a library for creating human-friendly identifiers, aka "slugs". It can
 also be useful for normalizing and sanitizing data.