Try to get a later version of certifi on travis for py27

.travis.yml

@@ -72,6 +72,8 @@ install:
 # pynbody, install deps with conda as much as possible
  - if $REQUIRES_PYNBODY; then conda install h5py pandas pytz; fi
  - if $REQUIRES_PYNBODY; then pip install git+git://github.com/pynbody/pynbody.git; fi
+# pytz install (I think) seems to downgrade certifi above, so update to newer version
+ - if $REQUIRES_PYNBODY && [[ $TRAVIS_PYTHON_VERSION == 2.7 ]]; then conda update certifi; fi
  # clone my version of the torus code, don't do this for one test, to make sure the code installs without the torus code
  - if [[ $TEST_FILES != 'tests/test_evolveddiskdf.py tests/test_jeans.py' ]]; then git clone https://github.com/jobovy/Torus.git galpy/actionAngle/actionAngleTorus_c_ext/torus; fi
  - if [[ $TEST_FILES != 'tests/test_evolveddiskdf.py tests/test_jeans.py' ]]; then cd galpy/actionAngle/actionAngleTorus_c_ext/torus; fi