Increment patch version to 0.4.2

Also, remove unused variable.
diff --git a/autoflake.py b/autoflake.py
index 973f2ae..832fa87 100644
--- a/autoflake.py
+++ b/autoflake.py
@@ -37,10 +37,7 @@
 import pyflakes.reporter
 
 
-__version__ = '0.4.1'
-
-
-PYFLAKES_BIN = 'pyflakes'
+__version__ = '0.4.2'
 
 
 ATOMS = frozenset([tokenize.NAME, tokenize.NUMBER, tokenize.STRING])