repo: move all source code in crates directory

The top-level listing was just getting a bit too long for my taste. So
put all of the code in one directory and shrink the large top-level mess
to a small top-level mess.

NOTE: This commit only contains renames. The subsequent commit will
actually make ripgrep build again. We do it this way with the naive hope
that this will make it easier for git history to track the renames.
Sigh.

crates/ignore/README.md

@@ -0,0 +1,66 @@
+ignore
+======
+The ignore crate provides a fast recursive directory iterator that respects
+various filters such as globs, file types and `.gitignore` files. This crate
+also provides lower level direct access to gitignore and file type matchers.
+
+[![Linux build status](https://api.travis-ci.org/BurntSushi/ripgrep.svg)](https://travis-ci.org/BurntSushi/ripgrep)
+[![Windows build status](https://ci.appveyor.com/api/projects/status/github/BurntSushi/ripgrep?svg=true)](https://ci.appveyor.com/project/BurntSushi/ripgrep)
+[![](https://img.shields.io/crates/v/ignore.svg)](https://crates.io/crates/ignore)
+
+Dual-licensed under MIT or the [UNLICENSE](http://unlicense.org).
+
+### Documentation
+
+[https://docs.rs/ignore](https://docs.rs/ignore)
+
+### Usage
+
+Add this to your `Cargo.toml`:
+
+```toml
+[dependencies]
+ignore = "0.4"
+```
+
+and this to your crate root:
+
+```rust
+extern crate ignore;
+```
+
+### Example
+
+This example shows the most basic usage of this crate. This code will
+recursively traverse the current directory while automatically filtering out
+files and directories according to ignore globs found in files like
+`.ignore` and `.gitignore`:
+
+
+```rust,no_run
+use ignore::Walk;
+
+for result in Walk::new("./") {
+    // Each item yielded by the iterator is either a directory entry or an
+    // error, so either print the path or the error.
+    match result {
+        Ok(entry) => println!("{}", entry.path().display()),
+        Err(err) => println!("ERROR: {}", err),
+    }
+}
+```
+
+### Example: advanced
+
+By default, the recursive directory iterator will ignore hidden files and
+directories. This can be disabled by building the iterator with `WalkBuilder`:
+
+```rust,no_run
+use ignore::WalkBuilder;
+
+for result in WalkBuilder::new("./").hidden(false).build() {
+    println!("{:?}", result);
+}
+```
+
+See the documentation for `WalkBuilder` for many other options.