require doctests to pass on travis-testin

Author: weikang9009

.travis.yml

@@ -45,7 +45,7 @@ install:
 script:
   - python setup.py sdist >/dev/null
   - python setup.py install
-  - nosetests --verbose --with-coverage --cover-package=spint;
+  - nosetests --verbose --with-doctest --with-coverage --cover-package=spint;
 
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