Summary:
With this change the getdeps' CargoBuilder will support depencies between cargo builds.

The way how it works is documented in the code and required few assumptions about how a cargo project has to be defined in order to support this.

This change also adds the "mononoke" manifest and few Cargo.toml files to the mononoke project to prove that this new feature works.

Reviewed By: farnz

Differential Revision: D19468912

fbshipit-source-id: f299733cbbc2ec7bca399c898ec8d710334d0fa9