Add the semicolon missing from the generated main.rs contents.

When you run `cargo new project-name --bin`, a project is generated by cargo
with a file, `src/main.rs`. This file has a main function with one line that
prints hello, world, but a semicolon is missing from the end of the
expression.
Implement -l/--list for `cargo package`

This provides a method of listing the files that will be in a package without
actually creating one.

Closes #855
auto merge of #845 : jbranchaud/cargo/add-missing-semicolon-for-new-project-main, r=alexcrichton

When you run `cargo new project-name --bin`, a project is generated by cargo
with a file, `src/main.rs`. This file has a main function with one line that
prints hello, world, but a semicolon is missing from the end of the
expression.
auto merge of #863 : alexcrichton/cargo/issue-855, r=huonw

This provides a method of listing the files that will be in a package without
actually creating one.

Closes #855