NF - python 3 building for travis-ci

After some futzing, work round virtualenvs to build and test nibabel
under Travis CI.  Needed to do `python setup.py install` for numpy, and
find 2to3 refactored tests in installation directory.

Author: matthew-brett

.travis.yml

@@ -3,9 +3,22 @@ language: python
 python:
     - "2.6"
     - "2.7"
+    - "3.2"
+env:
+    NUMPY_VER=1.6.1
+before_install:
+    - mkdir builds
+    - pushd builds
+    - curl -O http://pypi.python.org/packages/source/n/numpy/numpy-${NUMPY_VER}.tar.gz
+    - tar zxf numpy-${NUMPY_VER}.tar.gz
+    - cd numpy-${NUMPY_VER}
+    - python setup.py install
+    - popd
 # command to install dependencies, e.g. pip install -r requirements.txt --use-mirrors
 install:
-    - pip install numpy --use-mirrors
+    - python setup.py install
 # command to run tests, e.g. python setup.py test
 script:
-    - nosetests nibabel
+    # Change into an innocuous directory and find tests from installation
+    - cd doc
+    - nosetests `python -c "import os; import nibabel; print(os.path.dirname(nibabel.__file__))"`