Include leiningen dependencies when project.clj includes :eval-in-leiningen

[danielcompton]

This is more on the wishlist than the essential side, but it would be good if Cursive detected when you were writing a lein plugin and included leiningen's dependencies. At the moment things like https://github.com/jonase/lein-kibit/blob/master/src/leiningen/kibit.clj#L2 aren't able to be resolved as there isn't an explicit dependency on it in the project.clj.

Leiningen dependencies are included when :eval-in-leiningen is true in the project.clj. https://github.com/technomancy/leiningen/blob/master/doc/PLUGINS.md