Add ALLOW_MULTILINE_DICTIONARY_KEYS knob

This allows us to split a dictionary key over multiple lines, which is
something pylint doesn't like.
diff --git a/setup.py b/setup.py
index fc8781e..c73016b 100644
--- a/setup.py
+++ b/setup.py
@@ -64,5 +64,9 @@
           'Topic :: Software Development :: Libraries :: Python Modules',
           'Topic :: Software Development :: Quality Assurance',
       ],
-      entry_points={'console_scripts': ['yapf = yapf:run_main'],},
-      cmdclass={'test': RunTests,},)
+      entry_points={
+          'console_scripts': ['yapf = yapf:run_main'],
+      },
+      cmdclass={
+          'test': RunTests,
+      },)