Try to fix travis build.

Author: Sarah Mount

.travis.yml

@@ -17,7 +17,7 @@ install:
 - cd $TRAVIS_BUILD_DIR
 - export PYTHONPATH=${PYTHONPATH}:${HOME}/pydgin/
 script:
-- py.test -n 4 -rxs --color=yes --cov-config .coveragerc --cov=revelation revelation/test/ scripts/test/
+- py.test -rxs --color=yes --cov-config .coveragerc --cov=revelation revelation/test/ scripts/test/
 - mkdir bin
 - test "$TRANSLATE" == "true" && PYTHONPATH=${HOME}/pydgin/:${HOME}/pypy:. ${HOME}/pypy/rpython/bin/rpython
   --no-pdb --opt=jit revelation/sim.py || true