New things
* Polynomial division with a remainder with `divmod()`, e.g.
pycon
>>> p, r = divmod(Polynomial(1, 2, 3))
>>> p
Polynomial(1, 0)
>>> r
Polynomial(3)
* Floor division support (`//` and `//=`) (24)
* Modulo support (`%` and `%=`) (24)
* `**` and `pow()` support (32 )
* `<<`, `>>`, `<<=`, `>>=` support (31 )
* Method that calculates and returns the _n_-th derivative of the polynomial (`nth_derivative(n)`)
* Check if a term or a polynomial's terms all exist in another polynomial with `in` (27)
* Add `FrozenPolynomial` which is immutable (33)
Fixes things
* Fix `str()` output for terms with degrees with 10 to 19
* Fix 35 - handle degree changes and zero instance operations
* Fix derivative of zero (17 )
* Fix multiplying by zero (18 )
* Fix `Constant` to number casts (16)
* Fix default monomial value (15 )
* Fix bug when setting the leading term to zero (19)
* Fix `repr()` for Binomial and Trinomial (38)
* Simplified source code: module `polynomial` now divided into the following submodules: `core`, `binomial`, `trinomial`
* Optimize addition and multiplication performance (41)
Again, kudos to philippeitis for all the hard work!