ripgrep: migrate to libripgrep

This commit does the work to delete the old `grep` crate and effectively
rewrite most of ripgrep core to use the new libripgrep crates. The new
`grep` crate is now a facade that collects the various crates that make
up libripgrep.

The most complex part of ripgrep core is now arguably the translation
between command line parameters and the library options, which is
ultimately where we want to be.

globset/README.md

@@ -4,7 +4,7 @@ Cross platform single glob and glob set matching. Glob set matching is the
 process of matching one or more glob patterns against a single candidate path
 simultaneously, and returning all of the globs that matched.
 
-[![Linux build status](https://api.travis-ci.org/BurntSushi/ripgrep.png)](https://travis-ci.org/BurntSushi/ripgrep)
+[![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/globset.svg)](https://crates.io/crates/globset)
 

globset/src/lib.rs

@@ -470,7 +470,6 @@ impl GlobSetBuilder {
     }
 
     /// Add a new pattern to this set.
-    #[allow(dead_code)]
     pub fn add(&mut self, pat: Glob) -> &mut GlobSetBuilder {
         self.pats.push(pat);
         self