Poetry resolving dependencies is amazingly slow

• I am on the latest Poetry version.
• I have searched the issues of this repo and believe that this is not a duplicate.
• If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

• OS version and name: macOS 10.14
• Poetry version: 0.11.5
• Link of a Gist with the contents of your pyproject.toml file: https://gist.github.com/cprieto/b5996c4ffd2e77c7ab05253022c482bd

Issue

I just created a new project with poetry new and just added one package, petl, I was surprised when I found out in a new project (which includes pytest) it took over half an hour to install, yes, I know no cache was used, and yes, I know it has to download all the dependencies and handle their installation, but this time was insane.

I know this has been reported before in https://github.com/sdispater/poetry/issues/65 but maybe I am missing some discussion about how to improve this time, because honestly, waiting between 3min to 30min to install a package is too much, especially when the package size is small.

I included the output of my time poetry add -vvv petl command: https://gist.github.com/cprieto/ed5def2f51e8e16328770ebd76a6355e