Test CLI Applications

Currently, this crate only includes basic functionality to check the output of a child process is as expected.

Example

Here's a trivial example:

extern crate assert_cli;
assert_cli::assert_cli_output("echo", &["42"], "42").unwrap();

And here is one that will fail:

extern crate assert_cli;
assert_cli::assert_cli_output("echo", &["42"], "1337").unwrap();

this will show a nice, colorful diff in your terminal, like this:

-1337
+42