Use space_weather.nc instead of missing file and enabled doctests
Simplified ionosphere example. Closes #603.

Also includes PEP8 changes.
Merge pull request #728 from esc24/reducing_docs

Cube extraction doc examples
Modified cube dim_coords and aux_coords docstrings
Merge pull request #733 from esc24/dimcoord_doc

Modified cube dim_coords and aux_coords docstrings
Change zorder of contour lines drawn by contourf.

This addresses the issue of objects appearing in between the filled
and line contours drawn by contourf by reducing the difference in
zorder between the two.
Bugfix to DimCoord.from_regular
Merge pull request #732 from ajdawson/tec-simplify

Simplified ionosphere example.
Added example to iris.analysis.interpolate.linear docstring
Merge pull request #734 from esc24/from_reg_fix

From reg fix
Merge pull request #735 from esc24/linear_doc_example

Linear doc example
Updated the master version.
Added the magic lines.