relax constraint on faraday to build on newer rubies

[mknudsen]

implements suggestions from #19

[mknudsen]

Ah nevermind, I think this breaks the tests.

Lots of these

  58) Behance::Client::Wips#wip_revision_comments without parameters gets a list of comments
     Failure/Error: @comments = @client.wip_revision_comments(1, 2)
     NoMethodError:
       undefined method `close' for #<StubSocket:0x000000013bb065d0>
       Did you mean?  closed?
                      clone
     # ./lib/behance/client.rb:56:in `request'
     # ./lib/behance/wips.rb:71:in `wip_revision_comments'

[mknudsen]

I constrained the version of faraday middleware and fixed an issue faraday was complaining about. At least rspec runs now.