moved the hill equation to it's own function file hill.m, which
supports vectorialized parameters (well, at least one at a time).
So for example, the hill coeficient passed to it can be a list
like h=[a:b]. Same for vMax and k.

The main code for the homework is in a function file hillEQ.m,
which calls a local function to do all the work except for
chart titles.

WORKS in Octave, untested on MatLab.
trivial changes
Ensured MatLab compatibility: took out implicit broadcasting
in hill.m and and using bsxfun() for each operation (ugly).

Using better captions for figures now.
Checked MatLab compatibility for AutoReg. MatLab gives Warning when adding
figure legend.