Expose a context manager for histograms

[roncohen]

• Makes it a lot easier to use AppMetrics to time specific parts of the code
• Modifies the documentation a little, to make it clear that with_histogram will in fact "time" your code when used in a decorator.

[coveralls]

Coverage decreased (-0.04%) to 99.23% when pulling 0cca2e6 on roncohen:feature/contextmanager into a7ebbbe on avalente:master.

[coveralls]

Coverage increased (+0.0%) to 99.28% when pulling 5dd1925 on roncohen:feature/contextmanager into a7ebbbe on avalente:master.

[coveralls]

Coverage increased (+0.0%) to 99.28% when pulling 5dd1925 on roncohen:feature/contextmanager into a7ebbbe on avalente:master.

[avalente]

Hi,
I wouldn't pollute Histogram's interface, I'd rather use a function similar to with_histogram, probably with the same signature and semantic, something such as:

@contextmanager
def timer(name, reservoir_type="uniform", *reservoir_args, **reservoir_kwargs):
    # ... same stuff as with_historgram ...

    t1 = time.time()
    yield
    t2 = time.time()
    hmetric.notify(t2-t1)


it seems more clear to me, what do you think?

[roncohen]

I'm not a fan of the "with_histogram" interface that's why I put in on the Histogram. Of course, its up to you. I'll refactor.

[avalente]

Thank you. I prefer to keep the interfaces coherent as much as possible and push specificities out of the classes.