NF - allow weights in rolling window aggregations

Allowing weights to be used in rolling window aggregations means
that the rolling_window method of a cube can be used to apply
arbitrary digital filters.
Mod to coordinate names in NIMROD loader.
Update to test results.
NF - normalized area weights

Adds a keyword argument to normalize area weights by the total grid
area. Includes a simple test.
Merge pull request #286 from ajdawson/normalized-area-weights

NF - normalized area weights
Updated reference from basemap to cartopy in html
Removed all references to basemap. closes #177
made reference to pyproj under install
minor bug introduced in rebase
Merge pull request #290 from cpelley/new_rm_basemap

Docs still mention "Basemap" (new rm basemap)
xy grids from 2d coords
test
review actions
reverted class name
Merge pull request #207 from bblay/plot_2dxy

Plot 2dxy
Review actions.
rm incorrect dep of cart on pyproj, closes #177
rm superfluous sentence, related to closed PR #207
Merge pull request #302 from cpelley/update_missmerge

Missed points in previous merges
travis