Add PolarPlot

Use the pgfplots library `polar`.
Use 'polaraxis' instead of 'axis' for the plot environment.
Make the background grid less obvious.
Attempt to move the yaxis out of the graph area,
the tick marks are still at their original location..
this can probably be done nicer.
Added degree sign to x and y ticks

This should be the default for the x axis, but no for y.
So it should be made into an option.
Apparently inside is outside..

Polar plot == Hollow Earth?
Fix tick marks for y axis

Move the ticks to the axis line and make these ticks align to the
outside.
So for x ticks inside is outside, but for y ticks things are somewhat
normal.
Add function to choose an axis background color.
Add scatter plot function
Update docstrings, code style, and fix duplication
Remove default markstyle for scatter plot

Just use the TikZ default, just like plot.
Replace GraphArtist by Plot in demo files
Add polar version of the histogram plot

The use_steps option does not work properly in polar coordinates.
So instead build the steps manually.
Improve polar histogram

Add more points (one every .2 degrees) between bin edges,
this makes the ‘step-line’ follow the curvature.
Use fixed bins in the polar histogram demo (from 0 to 360),
otherwise the start and end were determined by the random numbers,
which don’t (always) include 0 and 360.
Rename demo output.
Remove text from docstring which is no longer true
Update version in docs to current release version

Add the GitHub description to the texinfo description..
Improve polar histogram

Improved polar histogram demo with extra cases:
One where the ends do not meet.
One where the range is beyond 360° and is fully connected.
Add tutorial to the docs to make a basic plot

Add example plots.
Add simple favicon.
Extra example plot for the README

From the demo_spectrum.py
Use rst syntax instead of markdown..
Include link to the script used to create the plot
Update demos

Move shower front demo data to data directory.
Add polar histogram demo to the Makefile and demo_plots.
Use tabs instead of spaces for the indentation in the Makefile
Allow setting of ticks suffixes e.g. ° and %

PolarPlot defaults to using ° as suffix for x (phi) ticks.