Cartopy: axis label - workaround

My (quite crude) work-around to this is detailed in this notebook: http://nbviewer.ipython.org/gist/ajdawson/dd536f786741e987ae4e

The notebook requires cartopy >= 0.12.

All I've done is find the intersection of the appropriate gridline with the map boundary. I've assumed the map boundary will always be rectangular, and I can only label the bottom and left sides. Hopefully this might be useful as something to build on.

I haven't tried it out myself, but I noticed in the salem package docs there being an ability to handle gridlines of other projections with their homegrown plotting utility, which doesn't change matplotlib's axes' projection.