Add .github/workflows/ci.yml

- Remove `.travis.yml`

.github/workflows/ci.yml

@@ -0,0 +1,32 @@
+on: push
+
+name: Build and test
+
+jobs:
+  build:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ ubuntu-latest, macos-latest, windows-latest ]
+        rust: [ stable ]
+
+    name: ${{ matrix.os }}, Rust ${{ matrix.rust }}
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Install Rust (rustup)
+      run: |
+        rustup update ${{ matrix.rust }} --no-self-update
+        rustup default ${{ matrix.rust }}
+        rustup component add rustfmt
+        rustc --version
+      shell: bash
+
+    - name: Build (release)
+      run: cargo build --verbose --release
+
+    - name: Check formatting
+      run: cargo fmt -- --check
+
+    - name: Test
+      run: cargo test

README.md

@@ -1,4 +1,4 @@
-[![Build Status](https://travis-ci.org/cruessler/git-tree.svg?branch=master)](https://travis-ci.org/cruessler/git-tree)
+[![Build Status](https://github.com/cruessler/git-tree/workflows/build/badge.svg)](https://github.com/cruessler/git-tree/actions?query=workflow%3Abuild)
 
 # git-tree