Stable version 0.4.3

This is purely a bugfix bump that works on GHC 7.6.3,
as currently found in Debian stable and Ubuntu LTS.

ShellCheck.cabal

 Name:             ShellCheck
-Version:          0.4.2
+Version:          0.4.3
 Synopsis:         Shell script analysis tool
 License:          GPL-3
 License-file:     LICENSE