Adding insertRow and insertColumn methods to Matrix

[twheys]

This is a useful addition to the Matrix class and compliments the removeRow and removeColumn methods.

[twheys]

to avoid confusion with the insert methods

[vkostyukov]

But this is definitely insert. If you mean insert(Matrix) methods then I don't think we will confuse things by insertRow/insertColumn methods. Moreover, they feel natural.

[twheys]

Alright, I'll update the names.

[vkostyukov]

Cool! Thanks @twheys!