Sort available lexers by its tag

When running `roughify list` I thought it might be useful to sort available lexers by its tag helping my eyes to find my favorite language :)

## Before

```bash
$ rougify | head -10
== Available Lexers ==
haml: The Haml templating system for Ruby (haml.info) [aliases: HAML]

elixir: Elixir language (elixir-lang.org)

prolog: The Prolog programming language (http://en.wikipedia.org/wiki/Prolog) [aliases: prolog]

smalltalk: The Smalltalk programming language [aliases: st,squeak]

make: Makefile syntax [aliases: makefile,mf,gnumake,bsdmake]
```

## After

```bash
$ rougify | head -10
== Available Lexers ==
c: The C programming language

clojure: The Clojure programming language (clojure.org) [aliases: clj,cljs]

coffeescript: The Coffeescript programming language (coffeescript.org) [aliases: coffee,coffee-script]

common_lisp: The Common Lisp variant of Lisp (common-lisp.net) [aliases: cl,common-lisp]

conf: A generic lexer for configuration files [aliases: config,configuration]
```

WDYT?

I'm happy to squash both commits.