Move rocket and iron integrations to separate crates

[theduke]

Since breaking changes in iron/rocket can force a major version bump to juniper, which is the case right now with the Rocket update (#67), we'd like to pull out the integrations into separate crates.

This also makes the testing setup a bit easier to handle.

Tasks

• Rocket

  • Move code to juniper_rocket crate
  • Move example to new crate
  • Update travis/appveyor specs
  • Documentation
  • Publish crate

• Iron

  • Move code to juniper_iron crate
  • Move example to new crate
  • Update travis/appveyor specs
  • Documentation
  • Publish crate

[theduke]

All that is left here is writing a guide about rocket for the book.

[shuaizhiwen]

I have been waiting for a better example of the rocket, so I really put juniper used in my project, I now use rocket + juniper + mongo to build my blog, but it seems that juniper and Mongo are not very good in my project, and look forward to a better rocket + juniper the example.