model.md issues

[pixelzoom]

Related to code review #259, where @samreid said:

I recommend to start with the documentation:
wave-interference/doc/implementation-notes.md
wave-interference/doc/model.md

Formatting of model.md is jacked, and it's unclear whether it was reviewed by @arouinfar.

[pixelzoom]

@samreid please review the formatting changes that I made above.

@arouinfar please review to verify that this contains all of the info that you'd like to communicate to a nontechnical audience.

[samreid]

Formatting changes look good, self-unassigning but leaving @arouinfar assigned to make sure the content is complete and correct.

[arouinfar]

Looks good to me. Thanks @pixelzoom @samreid!