RF: decorator to insist on matplotlib agg backend

Gael has his own matplotlib test machinery in the viz_tools, which
require the svg backend.  When this gets run first, the diagnostic
commands requiring png output will error out.  Switch to agg backend via
test decorator.
BF: make use of dot compatible with numpy < 1.5

Accidental use of A.dot(B) syntax.
BF: deal with random signs for PCA on Windows

Windows seems to give random signs for the PCA even across runs on the
same data; make sure tests don't fail because of this.
BF: set matplotlib backend for realign command

Unconstrained, raises a display error during testing.
BF: object deletion for Windows file delete errors

Getting Windows errors deleting temporary files; delete objects holding
onto files.
RF: allow for run-to-run difference in SVD results

On 32-bit, exploring SVD seems to confirm that the results differ
between runs at around 10**-10 precision.  Allow for this.
RF: make .travis.yml use travis Python and wheels

We were using erlang as language and apt-get for dependencies, because
of the difficulty getting numpy, scipy onto the travis slaves when using
the standard travis Python virtualenvs.

Now travis has numpy in the virtualenvs, and astropy, nipy.bic have
wheels for the travis slaves, so installation is much quicker.  This
commit switches back to using the travis Python testing machinery.
Merge pull request #319 from matthew-brett/update-travis-yml

RF: make .travis.yml use travis Python and wheels

We were using erlang as language and apt-get for dependencies, because of the
difficulty getting numpy, scipy onto the travis slaves when using the standard
travis Python virtualenvs.

Now travis has numpy in the virtualenvs, and astropy, nipy.bic have wheels for
the travis slaves, so installation is much quicker. This commit switches back
to using the travis Python testing machinery.
Merge remote-tracking branch 'upstream/master'