NF - add travis CI setup to repository

``.travis.yml`` file useful for automated testing on commits, on the
Travis-CI service.  Not current enabled for nipy/nibabel repository, but
useful for user repositories.

Author: matthew-brett

.travis.yml

@@ -0,0 +1,11 @@
+# vim ft=yaml
+language: python
+python:
+    - "2.6"
+    - "2.7"
+# command to install dependencies, e.g. pip install -r requirements.txt --use-mirrors
+install:
+    - pip install numpy --use-mirrors
+# command to run tests, e.g. python setup.py test
+script:
+    - nosetests nibabel