Fixed bug preventing G.strong_orientation() from working on G a multigraph, added a small multigraph to doctests
Improved caching in monsky_washnitzer.py
Added a category parameter to Module

This allows to set a more specific category than the default category of
modules/vector spaces. Also extended docstrings with a working example of a
module.
Merge branch 'develop' into ticket/16318
Trac #16251: Polynomials with unhashable coefficients should be unhashable

Currently, polynomials with unhashable coefficients ignore the
`TypeError` their coefficients raise:
{{{
sage: K.<a> = Qq(9)
sage: R.<t> = K[]
sage: hash(t)
Exception TypeError: "unhashable type:
'sage.rings.padics.padic_ZZ_pX_CR_element.pAdicZZpXCRElement'" in
'sage.rings.polynomial.polynomial_element.Polynomial._hash_c' ignored
0
}}}

URL: http://trac.sagemath.org/16251
Reported by: saraedum
Ticket author(s): Julian Rueth
Reviewer(s): Peter Bruin
Trac #16307: Fix small bug in G.strong_orientation()

Fix small bug in G.strong_orientation() by replacing
{{{d.has_edge(e[0].e[1]) }}}
with
{{{d.has_edge(e[0],e[1])}}}

The bug causes G.strong_orientation() to fail for G a multigraph.  Also
added a small multigraph to the doctests for G.strong_orientation()

URL: http://trac.sagemath.org/16307
Reported by: jdickinson
Ticket author(s): Jennet Dickinson
Reviewer(s): Nathann Cohen
Trac #16318: Improve some manual caching in monsky_washnitzer

This improves caching in preparation for #11895 by using
UniqueRepresentation
and cached_method in some places.

URL: http://trac.sagemath.org/16318
Reported by: saraedum
Ticket author(s): Julian Rueth
Reviewer(s): Peter Bruin
Trac #16328: Add a category parameter for Module

Currently, a `Module` (not to be confused with a `Module_old`) does not
have a `category` parameter to overwrite the default category
`Modules(base_ring)` with a more specific one. Such a parameter is
necessary, e.g., for porting Hecke modules to use `Module` instead of
`Module_old`.

URL: http://trac.sagemath.org/16328
Reported by: saraedum
Ticket author(s): Julian Rüth
Reviewer(s): Peter Bruin