Use setuptools if available.

Summary: Because working in a virtualenv w/ setuptools makes things a little easier :)

Test Plan: workon hg && python setup.py develop

Reviewers: rmcelroy, durham

Reviewed By: durham

Differential Revision: https://phabricator.fb.com/D2570341

Signature: t1:2570341:1445542319:0f30cb4aefb7c59753decda4535ca335a4f423cc

.hgignore

@@ -2,3 +2,4 @@
 \.so$
 \.err$
 ^build/
+^.*\.egg-info/

setup.py

@@ -1,4 +1,7 @@
-from distutils.core import setup, Extension
+try:
+    from setuptools import setup
+except ImportError:
+    from distutils.core import setup
 
 setup(
     name='fbhgext',