install doesn't fully respect -q parameter.

[goertzenator]

When I use the -q (quiet) parameter with the install command, I still get the following output:

cargo install --path crates/erl_comm/ --root priv/rust -q
be sure to add `/home/goertzen/rust.mk_demo/priv/rust/bin` to your PATH to be able to run the installed binaries

The expectation is to not see the be sure to add... line.

Use case: I am writing a plugin for Erlang to build extension modules in Rust. Cargo is too noisy during build:

goertzen@g550jk ~/rust.mk_demo $ make
 DEPEND rustmk_demo.d
 ERLC   complex1.erl rustmk_demo_app.erl rustmk_demo_sup.erl
 APP    rustmk_demo
 CARGO  erl_comm
be sure to add `/home/goertzen/rust.mk_demo/priv/rust/bin` to your PATH to be able to run the installed binaries

[alexcrichton]

Oops! Should be a pretty easy conditional to add somewhere though

[alexcrichton]

I think this is something like Shell::warn just needs a check like Shell::status has today (or something like that)