Use TF1 for keras tests (#94)

Fixes Travis build script

.travis.yml

@@ -8,7 +8,7 @@ jobs:
   - name: Keras 2.1.3
     env: KERAS_VERSION=2.1.3
   - name: Keras 2.2.3
-    env: KERAS_VERSION=2.2.2
+    env: KERAS_VERSION=2.2.3
   - name: Older Scikit-Learn
     env: SKLEARN_VERSION=0.19.1
 before_install:

test-requirements.txt

@@ -2,5 +2,4 @@ h5py>=2.8.0
 pandas>=0.22.0
 scikit-learn>=0.19.1
 scipy>=0.19.1
-tensorflow>=1.8.0
 torch>=1.1.0

travis/install.sh

@@ -7,15 +7,18 @@ pip install --upgrade pip setuptools wheel
 pip install -e .
 pip install coveralls flake8
 
+# Adding keras and TF1 for some tests
+if [ -n "$KERAS_VERSION" ]; then
+  pip install keras==$KERAS_VERSION "tensorflow<2"
+else
+  # Otherwise, use TF2
+  pip install "tensorflow>2"
+fi
+
 # Install the packages required for tests
 pip install -r test-requirements.txt
 pip install -r example-requirements.txt
 
-# Adding keras, an optional dependency
-if [ ! -z "$KERAS_VERSION" ]; then
-  pip install keras==$KERAS_VERSION
-fi
-
 # Manually-specifying the version of scikit-learn
 if [ ! -z "$SKLEARN_VERSION" ]; then
   pip install scikit-learn==$SKLEARN_VERSION