Fixed a list concatenation bug in changes made to setup.py

Author: tleonhardt

setup.py

@@ -63,7 +63,7 @@
 
 INSTALL_REQUIRES = ['pyparsing >= 2.0.1', 'pyperclip', 'six']
 if sys.platform.startswith('win'):
-    INSTALL_REQUIRES += 'pyreadline'
+    INSTALL_REQUIRES += ['pyreadline']
 
 # unittest.mock was added in Python 3.3.  mock is a backport of unittest.mock to all versions of Python
 TESTS_REQUIRE = ['mock', 'pytest']