Exposed yale_vector_insert_by_pos, which allows for fast insertion of
multiple non-diagonal items in a Yale matrix, provided that no resize is
required. This function does NOT do a lot of error checking, which is
why you have to specially indicate use of `NMatrix::YaleFunctions`. It
DOES update the IA pointer. It does NOT check that i and pos correspond.
Possible improvement: make pos optional, for when we're inserting an
entire row and don't need to do any seeking.

Also updated History, and fixed a typo in the docs.