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/matcher/README.md

@@ -0,0 +1,36 @@
+grep-matcher
+------------
+This crate provides a low level interface for describing regular expression
+matchers. The `grep` crate uses this interface in order to make the regex
+engine it uses pluggable.
+
+[![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/grep-matcher.svg)](https://crates.io/crates/grep-matcher)
+
+Dual-licensed under MIT or the [UNLICENSE](http://unlicense.org).
+
+### Documentation
+
+[https://docs.rs/grep-matcher](https://docs.rs/grep-matcher)
+
+**NOTE:** You probably don't want to use this crate directly. Instead, you
+should prefer the facade defined in the
+[`grep`](https://docs.rs/grep)
+crate.
+
+
+### Usage
+
+Add this to your `Cargo.toml`:
+
+```toml
+[dependencies]
+grep-matcher = "0.1"
+```
+
+and this to your crate root:
+
+```rust
+extern crate grep_matcher;
+```