Skip running coveralls on py2.5.

Thanks to https://gist.github.com/ssokolow/5496286

.travis.yml

@@ -9,11 +9,11 @@ python:
 
 install:
   - python setup.py install
-  - pip install coveralls --use-mirrors
+  - if [[ $TRAVIS_PYTHON_VERSION != '2.5' ]]; then pip install coveralls --use-mirrors && export HAS_COVERALLS=1; fi
 
 script:
   - sudo apt-get install -qq gdb
   - nosetests -q --with-coverage --cover-erase --cover-package=pyrasite
 
 after_success:
-  - coveralls
+  - if [[ $HAS_COVERALLS ]]; then coveralls; fi