CI allow_failures when testing on scikit-learn master (#370)

Author: glemaitre

.travis.yml

@@ -25,19 +25,24 @@ env:
     - MODULE=imblearn
     - OMP_NUM_THREADS=4
     - OPENBLAS_NUM_THREADS=4
-  matrix:
+
+matrix:
+  include:
     # This environment tests the using anaconda
     # Ubuntu 14.04 environment
-    - DISTRIB="ubuntu"
+    - env: DISTRIB="ubuntu"
     # Latest release
-    - DISTRIB="conda" PYTHON_VERSION="2.7"
-      NUMPY_VERSION="1.13.1" SCIPY_VERSION="0.19.1" SKLEARN_VERSION="0.19.0"
-    - DISTRIB="conda" PYTHON_VERSION="3.5"
-      NUMPY_VERSION="1.13.1" SCIPY_VERSION="0.19.1" SKLEARN_VERSION="0.19.0"
-    - DISTRIB="conda" PYTHON_VERSION="3.6"
-      NUMPY_VERSION="1.13.1" SCIPY_VERSION="0.19.1" SKLEARN_VERSION="0.19.0"
-    - DISTRIB="conda" PYTHON_VERSION="3.6"
-      NUMPY_VERSION="1.13.1" SCIPY_VERSION="0.19.1" SKLEARN_VERSION="master"
+    - env: DISTRIB="conda" PYTHON_VERSION="2.7"
+           NUMPY_VERSION="1.13.1" SCIPY_VERSION="0.19.1" SKLEARN_VERSION="0.19.0"
+    - env: DISTRIB="conda" PYTHON_VERSION="3.5"
+           NUMPY_VERSION="1.13.1" SCIPY_VERSION="0.19.1" SKLEARN_VERSION="0.19.0"
+    - env: DISTRIB="conda" PYTHON_VERSION="3.6"
+           NUMPY_VERSION="1.13.1" SCIPY_VERSION="0.19.1" SKLEARN_VERSION="0.19.0"
+    - env: DISTRIB="conda" PYTHON_VERSION="3.6"
+           NUMPY_VERSION="1.13.1" SCIPY_VERSION="0.19.1" SKLEARN_VERSION="master"
+  allow_failures:
+    - env: DISTRIB="conda" PYTHON_VERSION="3.6"
+           NUMPY_VERSION="1.13.1" SCIPY_VERSION="0.19.1" SKLEARN_VERSION="master"
 
 install: source build_tools/travis/install.sh
 script: bash build_tools/travis/test_script.sh