TST: install dependencies with Conda on py3.6.

Cover dependency installation via Conda in one of the tests.

Author: tswast

.travis.yml

@@ -31,8 +31,12 @@ install:
       conda install pandas=$PANDAS;
     fi
   - pip install coverage pytest pytest-cov flake8 codecov
-  - REQ="ci/requirements-${PYTHON}-${PANDAS}.pip"
-  - pip install -r $REQ
+  - REQ="ci/requirements-${PYTHON}-${PANDAS}"
+  - if [ -f "$REQ.pip" ]; then
+      pip install -r "$REQ.pip";
+    else
+      conda install --file "$REQ.conda";
+    fi
   - conda list
   - python setup.py install