implement method of lines

[jkingslake]

An approach to coupling the ice and hydro code could be to solve both with the method of lines (MOL). This should circumvent road blocks @glugeorge has been encountering with not finding python solvers capable of implementing the methods used in https://github.com/aarobel/SSAsimpleM and https://github.com/aarobel/SSAsimpleJ.

As a starting point to understand the method and eventually implement it with both sets of equations:

1. You can look at some code @rmskarbek and I wrote which uses the method of lines to solve a firn compaction model. The model is setup with FirnSetup5.m and run with FCM9b.m.

2. You can also look at the method section of the submitted paper (hopefully it will soon appear on Cryosphere Discussions, so it's not a problem sharing it here).
   Kingslake_firn_submitted.pdf
   Also look at Appendix B for a few more details on the method.

3. There are many good onine resources on the MOL, e.g., http://www.scholarpedia.org/article/Method_of_lines