Raise the minimum version of bitflags to 1.1
Raise the minimum version of bitflags to 1.1

This prevents warnings about "try! is deprecated" when using the latest
compiler and -Zminimal_versions.

asomers/nix,carllerche/nix-rust,nix-rust/nix,asomers/nix,carllerche/nix-rust,geofft/nix-rust,geofft/nix-rust,nix-rust/nix,carllerche/nix-rust,geofft/nix-rust