Summary:
This should fix the Travis CI builds. It adds rust toolchain support inside docker and sets the required THRIFT env variable.
Pull Request resolved: https://github.com/facebookexperimental/rust-shed/pull/3

Reviewed By: krallin

Differential Revision: D18905608

Pulled By: lukaspiatkowski

fbshipit-source-id: 5db1eff6f215a6617d8acaa0c99a62d45225956b