support non-modules in @require

[minrk]

Functions and other objects can be passed, which implies a push when the function is passed to apply.

This relieves one of the most common complaints in IPython.parallel - allowing multi-function tasks without a push call for the intermediate functions.

def foo(a):
    return a*a

@parallel.require(foo)
def bar(b):
    return foo(b)

@parallel.require(bar)
def baz(c, d):
    return bar(c) - bar(d)

view.apply_sync(baz, 4, 5)

Pinging @ogrisel as the source of the idea at PyData.

[ogrisel]

It looks good to me. I would like to pull from your branch to give it a try but the Hyatt wifi is failing me...

[jankatins]

related to #2489 ?

[minrk]

This is not really related to #2489, other than being an improvement in what objects can be sent and when.

[ellisonbg]

I have ran the test suite locally under python 2.7 (passed), tried some examples in the notebook and looked through the code. Looks like a nice improvement. I am +1 on merging.