Remove usage of d2to1

d2to1 pulls in setuptools, which trips the unhappy bugs with setuptools
updating. Move past that and just use new pbr.

Change-Id: I2609eda10ed781116940c3607ff85a14fc4b7f58
diff --git a/setup.py b/setup.py
index 59a0090..c0a24ea 100644
--- a/setup.py
+++ b/setup.py
@@ -17,5 +17,5 @@
 import setuptools
 
 setuptools.setup(
-    setup_requires=['d2to1', 'pbr'],
-    d2to1=True)
+    setup_requires=['pbr'],
+    pbr=True)