Speed up imports

[hallacy]

Removes pandas (no resource uses it) and fixes aiohttp importing as suggested in #380.

I think this gets us from ~5 seconds to 2.5 seconds:

[hauntsaninja]

This looks great!

re: #380 (comment)
I think fine to split up the helpers. If you end up needing to do something more general, could use a nice module __getattr__:

# lazy.py
def __getattr__(name):
    if name == "np":
        import numpy  # TODO: raise the nice MissingDependencyError
        globals()["np"] = numpy
        return numpy
    ...

and then use lazy.np everywhere you'd use np.

[elanzini]

@hallacy Was curious about what tool you used to get the visualization above.

[hauntsaninja]

Looks like tuna? I've seen some accuracy issues using tuna, I recommend one of these two: #380 (comment)

[elanzini]

Looks like tuna? I've seen some accuracy issues using tuna, I recommend one of these two: #380 (comment)

Thanks @hauntsaninja. From the README of tuna it sounds like it's also compatible with importtime, you just save the log locally and parse it with tuna.