ci: Add GitHub Actions

As part of this, changed tests import
This was also pointed out in #1

Author: jarofgreen

.github/workflows/ci.yml

@@ -0,0 +1,22 @@
+name: CI
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: [3.5, 3.6, 3.7, 3.8]
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-python@v1
+      with:
+        python-version: ${{ matrix.python-version }}
+    - uses: actions/cache@v1
+      with:
+        path: ~/.cache/pip
+        key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements_dev.txt') }}
+        restore-keys: |
+          ${{ runner.os }}-pip-
+    - run: pip install -e .[dev]
+    - run: python -m unittest discover

json_merge_patch/tests.py

@@ -1,5 +1,5 @@
 import unittest
-import lib as merge
+import json_merge_patch.lib as merge
 from collections import OrderedDict
 
 fixtures = [