Adds GH actions. (#346)

- adds ruby 3.0.0
- removes 2.4.10 tests
- adds changelog entry
- removes travis.yml

.github/dependabot.yml

@@ -0,0 +1,14 @@
+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://help.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+
+version: 2
+updates:
+  - package-ecosystem: "bundler" # See documentation for possible values
+    directory: "/" # Location of package manifests
+    schedule:
+      interval: "weekly"
+      day: "friday"
+    assignees:
+      - "LeFnord"

.github/workflows/rubocop.yml

@@ -0,0 +1,20 @@
+name: Rubocop
+
+on: push
+
+jobs:
+  rubocop:
+    name: Rubocop
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-ruby@v1
+        with:
+          ruby-version: '3.0'
+      - run: gem install rubocop --no-doc
+      - run: rubocop --format progress --format json --out rubocop.json
+        id: rubocop
+      - uses: duderman/rubocop-annotate-action@v0.1.0
+        with:
+          path: rubocop.json
+        if: ${{ failure() }}

.github/workflows/ruby.yml

@@ -0,0 +1,26 @@
+name: Ruby
+
+on:
+  push:
+    branches:
+      - '*'
+  pull_request:
+    branches:
+      - '*'
+
+jobs:
+  spec:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        ruby-version: ['2.6', '2.7', '3.0', head, jruby, truffleruby]
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ matrix.ruby-version }}
+        bundler-cache: true
+    - name: Run rspec
+      run: bundle exec rspec

grape-entity.gemspec

@@ -14,7 +14,7 @@ Gem::Specification.new do |s|
   s.description = 'Extracted from Grape, A Ruby framework for rapid API development with great conventions.'
   s.license     = 'MIT'
 
-  s.required_ruby_version = '>= 2.4'
+  s.required_ruby_version = '>= 2.5'
 
   s.add_runtime_dependency 'activesupport', '>= 3.0.0'
   # FIXME: remove dependecy