Auto merge of #859 - RalfJung:cargo, r=RalfJung
Auto merge of #859 - RalfJung:cargo, r=RalfJung

travis: do not install cargo from master

This tests the rpath hackery in `./miri`.

rust-lang/miri,tsion/miri,rust-lang/miri,rust-lang/miri,rust-lang/miri