[travis] attempt to test against both pandas 0.14 and 0.15, in preparation for handling the Categorical rewrite

Author: njsmith

.travis.yml

@@ -4,6 +4,13 @@ python:
   - 2.7
   - 3.3
   - 3.4
+matrix:
+  include:
+    # 0.14.0 is the last version with the old categorical system
+    - python: 3.3
+      env: PANDAS_VERSION_STR="=0.14.0"
+    - python: 2.7
+      env: PANDAS_VERSION_STR="=0.14.0"
 # This disables sudo, but makes builds start much faster
 # See http://blog.travis-ci.com/2014-12-17-faster-builds-with-container-based-infrastructure/
 sudo: false
@@ -18,8 +25,9 @@ before_install:
   - conda config --set always_yes yes --set changeps1 no
   - conda update -q conda
   - conda info -a
-  - conda create -q -n testenv python=$TRAVIS_PYTHON_VERSION numpy scipy pandas coverage nose pip
+  - conda create -q -n testenv python=$TRAVIS_PYTHON_VERSION numpy scipy coverage nose pip
   - source activate testenv
+  - conda install pandas${PANDAS_VERSION_STR}
 install:
   - python setup.py sdist
   - pip install dist/*