Fix null provider config

[jvliwanag]

• Defaults to NettyAsyncHttpProviderConfig which
  can be made to use unix sockets

Looks like this is null by default when running outside of SBT.

[softprops]

i'm actually surprised this can be null. This modifies the default config provided by dispatch. It's it possible there is a bug upstream?

[andypetrella]

FYI: this indeed fixed #14.
But yeah, it might be a upstream crap :-S

[andypetrella]

Would it be really problematic to merge this PR? Since it impacts quite importantly the usability of the project in certain env?
I mean, this is a great work that I'll love to use, but for now I'm stuck with a local build and I don't want to fork :-(.
Thanks for considering it.
cheers,
andy

[juanjovazquez]

Hi all,

I had a similar problem as it was described by @jvliwanag but in my case the stacktrace was slightly different. That problem was fixed by this PR applied on my own fork. So, this PR is a must IMHO. Now, I'm stuck with another issue. I'll open another thread #18 to deal with that. Thanks.