Update popular languages

I took all non-fork repositories on github.com, grouped them by their
primary language, and took the 25 most popular.

lib/linguist/popular.yml

@@ -9,21 +9,21 @@
 - CSS
 - Clojure
 - CoffeeScript
-- Common Lisp
-- Diff
-- Emacs Lisp
-- Erlang
+- Go
 - HTML
 - Haskell
 - Java
 - JavaScript
 - Lua
+- Matlab
 - Objective-C
 - PHP
 - Perl
 - Python
+- R
 - Ruby
-- SQL
 - Scala
-- Scheme
 - Shell
+- Swift
+- TeX
+- VimL