Improve readme

README.md

 # Projection matrix plot
 
-A `corner` plot for an array of dependent values
+A corner plot for an array of dependent values
 
 Given an `N` dimensional set of data (i.e. some function evaluated over a grid
 of coordinates), plot all possible 1D and 2D projections in the style of a
-[`corner` plot](http://corner.readthedocs.io/en/latest/pages/quickstart.html).
+["corner" plot](http://corner.readthedocs.io/en/latest/pages/quickstart.html).
 
 # Example