Print crate dependencies

[pravic]

cc #14

Note that it requires merge and publish of the https://github.com/g-k/g-k-crates-io-client first (and change of Cargo.toml).

This PR introduces a new option named --dependencies that prints the crate's dependencies (of the latest version):

$ cargo show time --dependencies

id: time
name: time
description: Utilities for working with time-related functions in Rust.
...
max_version: 0.1.40
...
dependencies:
libc ^0.2.1
log ^0.4
redox_syscall ^0.1
winapi ^0.3.0
winapi ^0.3.0
rustc-serialize ^0.3

[g-k]

Thanks! Looks good. Much cleaner with the map_err, ?, and eprintln. 👍

Left a comment about quieter output if you want to do that, otherwise just need to switch to the published crates client version like you mentioned.

[g-k]

merged your PR and published 0.16.0: https://crates.io/crates/g-k-crates-io-client/0.16.0 so this can be updated to that version.

[g-k]

If you'd rather have quieter output, I'd be OK with just printing just the id or name or both with the dependents instead of the full metadata.

[g-k]

I also need to remember to document how --json and --dependencies works.

[pravic]

I don't know how to combine 2 json responses into one output. May be --dependencies --json will print output from the /crates/$krate/$version/dependencies only?

I mean,
cargo show krate --json will print a response from the /crates/$krate
cargo show krate --dependencies --json will print another response from the /crates/$krate/$version/dependencies.

As for the brief output.. It is better to make it in another PR I think.

[pravic]

Also we need to distinguish dev (build-time) from normal and optional from direct dependencies.

This?

dependencies:
serde_derive ^1.0 (opt)
serde_derive ^1.0 (dev)

[g-k]

Thanks! This looks good. I opened issues for deciding what to do about the other stuff.