Mention ask_update.py in docstring of compute_known_facts()
Move logic out of sympy/assumptions/handlers/__init__.py
Use CommonHandler's AlwaysTrue/AlwaysFalse
Add sympy/assumptions/handlers/__init__.py
Add nonpositive/nonnegative predicates/handlers
Add fuzzy_or
Add zero predicate to the new assumptions system

Even though zero = ~nonzero & real exactly, this ended up being more work than
it should have been.
Don't assume that oo is real in the sets.

In the new assumptions, it won't be. Because of the singleton Reals, which is
created at import time, this is needed to make SymPy import at all in #2210.
Misc formatting in ask.py
Misc formatting issues in sympy/assumptions/handlers
Fix some instances of fuzzy_and and fuzzy_or not taking an iterable
Fix fuzzy_and and fuzzy_or to take args, not *args

    Also, fuzzy_and and fuzzy_or returns, accordingly, True and
    False for empty [].
Merge pull request #2399 from skirpichev/assumptions

assumptions, pr1