PPSD: enable getting/plotting mode and mean psd values
Update outdated matplotlib URIs.
Update NumPy website.
Update official Python URIs.
Update SciPy links.
Update IRIS hosted URIs.
Update geopy URI.
Make PyPI links HTTPS.
Fix links to source files.
Update URIs that are redirecting.
Update URIs that are now 404.
Fix threading test that sporadically fails on Travis.

threading.active_count will return the number of threads that would be
returned by threading.enumerate. These may include additional worker
threads that are unrelated to the user-spawned threads, and would cause
the loop to continue to wait even though all user-spawned threads were
totally complete.
add missing symbol curr_file to .def file
More resilient StationXML parser.

It now pops a warning when it cannot convert some string to a float or
the float is a NaN. It does not stop parsing anymore. This is
unfortunately needed for some real data out there.
Don't install suds-jurko on Travis.

It doesn't appear that the NERIES client is tested on Travis, so this
import is not needed.
Pin NumPy and SciPy to versions in the wheelhouse.

Matplotlib 1.3.1 and NumPy 1.9.0 are incompatible (so it surprises me
that they'll both install), and cause test failures.
Don't install M2Crypto on Travis.

It's used by Arclink, but not tested.
Add M2Crypto to EXTRA_REQUIRES.

Not sure why it hasn't been mentioned before.
Remove extra parentheses in print function calls.
Replacing GPL spline code by LGPL spline code

Now using the LGPL SPLINE library
http://people.sc.fsu.edu/~jburkardt/c_src/spline/spline.html

Adding an extra test, as the current obspy tests do not seem
to cover the interpolation part.

See #827.