Add dependency header in default Cargo.toml

[johshoff]

Almost any project beyond "hello world" will have some dependencies.
Including the [dependencies] header by default makes this slightly
simpler.

For new users of the language, this can potentially save some
frustration since crates.io currently does not mention the header, just
the line that goes beneath it.

For all users, this makes adding the first dependency to a project less
of a special case than to subsequent dependencies.

[rust-highfive]

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[steveklabnik]

Yeah, I've been thinking about this too. I think I'm 👍

[alexcrichton]

I wonder if it may be a good idea as well to pre-generate an annotated Cargo.toml? For example this could provide a commented out example of how to depend on some common crates like libc or rand. It could also just have an example of "Here's how you depend on a git repo" or "here's how you depend on crates.io" with a dummy package.

[steveklabnik]

I'm torn. We did that for a while with Bundler, but then you end up just deleting it anyway....

[alexcrichton]

Hm that's true, seems fine in that case to me!

@bors: r+ e708411

[bors]

⌛ Testing commit e708411 with merge 6026a18...

[bors]

☀️ Test successful - cargo-linux-32, cargo-linux-64, cargo-mac-32, cargo-mac-64, cargo-win-gnu-32, cargo-win-gnu-64, cargo-win-msvc-32, cargo-win-msvc-64