improve description for cargo install

Author: collin5

src/bin/cargo/cli.rs

@@ -206,7 +206,7 @@ Some common cargo commands are (see all commands with --list):
     update      Update dependencies listed in Cargo.lock
     search      Search registry for crates
     publish     Package and upload this package to the registry
-    install     Install a Rust binary
+    install     Install a Rust binary. Default location is $HOME/.cargo/bin
     uninstall   Uninstall a Rust binary
 
 See 'cargo help <command>' for more information on a specific command.\n",

src/bin/cargo/commands/install.rs

@@ -6,7 +6,7 @@ use cargo::util::ToUrl;
 
 pub fn cli() -> App {
     subcommand("install")
-        .about("Install a Rust binary")
+        .about("Install a Rust binary. Default location is $HOME/.cargo/bin")
         .arg(Arg::with_name("crate").empty_values(false).multiple(true))
         .arg(
             opt("version", "Specify a version to install from crates.io")