Update Changelog

CHANGELOG.md

 changelog
 ===========
+Version 0.5.4 (Nov 3, 2013)
+-----------------------------
+
+* Update lexers file
+
+Version 0.5.3 (Sep 17, 2013)
+-----------------------------
+
+* Fixes for Slash lexer
+* Improve highlighting for Slash lexer
+* Upgrade to latest pygments (1.7, changes summary follows.  See pygments changelog for details)
+  * Add Clay lexer
+  * Add Perl 6 lexer
+  * Add Swig lexer
+  * Add nesC lexer
+  * Add BlitzBasic lexer
+  * Add EBNF lexer
+  * Add Igor Pro lexer
+  * Add Rexx lexer
+  * Add Agda lexer
+  * Recognize vim modelines
+  * Improve Python 3 lexer
+  * Improve Opa lexer
+  * Improve Julia lexer
+  * Improve Lasso lexer
+  * Improve Objective C/C++ lexer
+  * Improve Ruby lexer
+  * Improve Stan lexer
+  * Improve JavaScript lexer
+  * Improve HTTP lexer
+  * Improve Koka lexer
+  * Improve Haxe lexer
+  * Improve Prolog lexer
+  * Improve F# lexer
+
+Version 0.5.2 (July 17, 2013)
+-----------------------------
+
+* Add Slash lexer
+
 Version 0.5.1 (June 25, 2013)
 -----------------------------