Catch Hackney errors using '{:error, reason}' tuple format

[luizvarela]

This will fix #117

This PR tries to fix the errors raised by Hackney, when we try to send a get request to an empty URL an exception is raised:

iex(1)> HTTPoison.get(" ")
** (exit) :badarg
       (kernel) gen_tcp.erl:148: :gen_tcp.connect/4
      (hackney) src/hackney_connect.erl:245: :hackney_connect.do_connect/5
      (hackney) src/hackney_connect.erl:36: :hackney_connect.connect/5
      (hackney) src/hackney.erl:328: :hackney.request/5
    (httpoison) lib/httpoison/base.ex:396: HTTPoison.Base.request/9

So, would be nice to return {:error, reason} for all these errors.
For example:

iex(1)> HTTPoison.get(" ")

{:error, %HTTPoison.Error{id: nil, reason: :badarg}}

[edgurgel]

Thanks for the PR! I don't "love" catching all the errors but it will be consistent with our API.

[edgurgel]

🎉 <3

[luizvarela]

Thanks @edgurgel 👍