clean up LMB + SP example
clean up LMB + SP example

The doctests demonstrating integration of the LakeMapperBarnes and the
FastscapeEroder are now robust, and hopefully much clearer.

cmshobe/landlab,landlab/landlab,amandersillinois/landlab,cmshobe/landlab,amandersillinois/landlab,cmshobe/landlab,landlab/landlab,landlab/landlab