Extend the documentation of the nalgebra integration to discuss its likely surprising memory layout requirements.

[adamreichold]

Closes #413

[adamreichold]

@Ruhrpottpatriot Could you have a look at the extended documentation here whether this would have answered your questions? Thanks.

[Ruhrpottpatriot]

This pretty much explains what I'd expect from the docs. You made three typos that should be fixed, but I marked the lines in question.