Pin sphinx version to 1.2 in tests.

Sphinx 1.2.1 has a bug that breaks our build:
https://bitbucket.org/birkenfeld/sphinx/pull-request/212/fix-an-exception-introduced-by/diff

.travis.yml

@@ -15,7 +15,7 @@ install:
     # always install unittest2 on py26 even if $DEPS is unset
     - if [[ $TRAVIS_PYTHON_VERSION == '2.6' ]]; then pip install --use-mirrors unittest2; fi
     - if [[ $TRAVIS_PYTHON_VERSION == 2* && $DEPS == true ]]; then pip install --use-mirrors futures mock pycares 'pycurl<7.19.3' twisted Monotime==1.0; fi
-    - if [[ $TRAVIS_PYTHON_VERSION == '2.7' && $DEPS == true ]]; then pip install --use-mirrors sphinx; fi
+    - if [[ $TRAVIS_PYTHON_VERSION == '2.7' && $DEPS == true ]]; then pip install --use-mirrors sphinx==1.2; fi
     - if [[ $TRAVIS_PYTHON_VERSION == 'pypy' && $DEPS == true ]]; then pip install --use-mirrors futures mock; fi
     - if [[ $TRAVIS_PYTHON_VERSION == '3.2' && $DEPS == true ]]; then pip install --use-mirrors pycares mock; fi
     - if [[ $TRAVIS_PYTHON_VERSION == '3.3' && $DEPS == true ]]; then pip install --use-mirrors pycares; fi

tox.ini

@@ -218,6 +218,6 @@ setenv = LANG=en_US.utf-8
 [testenv:py2-docs]
 basepython = python2.7
 changedir = docs
-deps = sphinx
+deps = sphinx==1.2
 commands =
     sphinx-build -q -E -n -W -b html . {envtmpdir}/html