Adding GitHub actions.

Signed-off-by: Tim 'mithro' Ansell <me@mith.ro>

.github/workflows/ci.yml

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..04e258c
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,28 @@
+name: CI tests
+
+on: [push, pull_request]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: [3.6, 3.7, 3.8, 3.9]
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Setup
+      run: |
+        sed -i -e's/- python/- python=${{ matrix.python-version }}/' environment.yml
+        cat environment.yml
+        # FIXME: #65 - Replace with `make-env`
+        ./prepareenv.sh
+    - name: Test
+      run: |
+        source "$HOME/miniconda/etc/profile.d/conda.sh"
+        conda activate yosys-env
+        which python
+        python --version
+        which tox
+        TOXENV="$(echo py${{ matrix.python-version }} | sed -e's/\.//g')" tox

.travis.yml

diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 9f8b7fa..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,20 +0,0 @@
-language: python
-
-python:
-  - 3.6
-  - 3.7
-  - 3.8
-  - 3.9
-
-install:
-  - source prepareenv.sh
-  - ./.github/travis/check_license.sh
-  - ./.github/travis/check_python_script.sh
-
-script:
-  - conda activate yosys-env
-  - which tox
-  - TOXENV="py${TRAVIS_PYTHON_VERSION//./}" tox
-
-notifications:
-  email: false