Update README since it mostly works now

# cargo doc-coverage

🚨 Warning! Doesn't work the way I want it to yet! 🚨

This crate does print out the percentage of public items that have

documentation. Unfortunately, it prints out the cumulative results after *each*

item that gets linted. The last result has the over all coverage, but I can't

figure out how to print this info only once after running the entire lint

rather than after every item.

This crate prints out the percentage of public items that have documentation.

## Installation and usage

I have gotten this to work with `rustc 1.15.0-nightly (d9bdc636d 2016-11-24)`. Assuming you use [rustup][], get on that nightly and install this plugin with the following commands:

I have gotten this to work with `rustc 1.15.0-nightly (d9bdc636d 2016-11-24)`.

Assuming you use [rustup][], get on that nightly and install this plugin with

the following commands:

```

$ rustup toolchain install nightly-2016-11-25

If you don't see any output, try doing a `cargo clean` or making a change in

your code to trigger a recompile.

What you should see is WAY TOO MUCH OUTPUT:

What you should see:

```

$ cargo doc-coverage

warning: 1 items, 1 undocumented, 0% documented

warning: 1 items, 1 undocumented, 0% documented

warning: 1 items, 1 undocumented, 0% documented

warning: 1 items, 1 undocumented, 0% documented

warning: 1 items, 1 undocumented, 0% documented

warning: 1 items, 1 undocumented, 0% documented

.....lots more.........

   Compiling nom v2.0.1 (file:///Users/carolnichols/rust/nom)

warning: 225 items, 117 undocumented, 48% documented

warning: 37 items, 15 undocumented, 59.45945945945946% documented

warning: 37 items, 15 undocumented, 59.45945945945946% documented

warning: 37 items, 15 undocumented, 59.45945945945946% documented

warning: 37 items, 15 undocumented, 59.45945945945946% documented

    Finished debug [unoptimized + debuginfo] target(s) in 0.77 secs

```

## Help

### Help

#### Help

If you know how I can hook into the linting system to output something only once when a lint is completely done, please let me know :)

## Inspiration/where most of this code came from

A large part of this code is from [clippy][] and the [rustc missing-docs lint][].