Auto merge of #3283 - saschagrunert:master, r=alexcrichton

Changed try! macros to ? operator

Since the stabilization of the ? operator (release 1.13.0)
the ? operator should be used to use idiomatic Rust.

diff --cc src/cargo/core/resolver/mod.rs
Simple merge

diff --cc tests/cargotest/support/mod.rs
Simple merge