FIX: sphinx init file now reads version info from version file.

This way, the version is only coded in the one wradlib/version file. Version
information in both setup.py and in doc/source/__init__.py is retrieved from that
file.

DOC: fixed external links, which gave a 404.

FIX: Made plot in docstring example for ipol function interpolate interactive.

Otherwise Codeship appears not to finish the tests waiting on the figure to be closed.

FIX: Fixed example with missing data in atten module function correctAttenuationHJ.

FIX: Also removed dummy functions from the other gabella function docstrings.

Reasonable examples should be provided in the future. However, I think it is not good
if dummy examples appear in the public library reference.

FIX: Removed dummy example from filter_gabella_b docstring.

FIX: Removed some examples from util funtion docstrings which did not really correspond to the functions.

That was the case for mean_over_time_windows and average_over_time_windows.

Also remove some blank lines from otehr examples in util.

By the way, these timeseries functions are a mess and I really need to clean them up....

FIX: Removed the specific version of Sphinx in the requirements.

Fixing the version of Sphinx in requirements.txt (as done in revision 690)
was probably not a good idea. The current Sphinx version seems to cause problems
on Codeship, but has not been reported to cause problems elsewhere....

FIX: With the new filter_window_polar the filter_cloudtype shuld only receive a float as scale.

Before, the scale argument had to be a tuple, with the new polar filtering, it is
only a float that corresponds to the range scale.

FIX: This recipe should not throw an error in case the data is not available.

Instead, a warning will be printed and the rest of the code will run with zeros as
input values.

FIX: Removed this example file because it only examplifies highly deprecated functions.

FIX: Reduced the size of an array that produced a MemoryError.

FIX: Changed keyword projstr to proj in calls of plot_ppi and plot_ppi_crosshair.

FIX: An error occurs when a specific matplotlib version is used due to a bug in matplotlib.

The fix checks for the matplotlib version. If matplotlib 1.2.1 is installed,
a message is printed into the figure.

See https://github.com/matplotlib/matplotlib/pull/1985 for details on the bug.

FIX: Fixed name of the data file.

MIN: Added a specific version number for Shpnix in requirements file.

The new requirements.txt specify 1.2.3 as Sphinx version. This is because it
turned out that newer Sphinx versions caused problems on Codeship.

Merged wradlib/wradlib into default

Merged in egouden/wradlib/feature/eg/gabella_polar (pull request #39)

filter_window_distance

DOC: Fixed a typo and removed some attenuation functions from the API documentation.

We should still think about what to do with these functions. But I thought removing
them from the documentation would be a first step. Right now, I would always recommend...

ENH: Added a companion example file with additonal data that can also serve as a test.

The example (attenuation_correction_example.py) has the same content as the tutorial.
Just the code is organised a little different.