Fix versioneer to update versions on install

versioneer.py

@@ -83,7 +83,7 @@ To use it:
 import os, sys, re
 from distutils.core import Command
 from distutils.command.sdist import sdist as _sdist
-from distutils.command.build import build as _build
+from distutils.command.build_py import build_py as _build_py
 
 versionfile_source = None
 versionfile_build = None
@@ -578,11 +578,10 @@ class cmd_version(Command):
         ver = get_version(verbose=True)
         print("Version is currently: %s" % ver)
 
-
-class cmd_build(_build):
+class cmd_build_py(_build_py):
     def run(self):
         versions = get_versions(verbose=True)
-        _build.run(self)
+        _build_py.run(self)
         # now locate _version.py in the new build/ directory and replace it
         # with an updated value
         target_versionfile = os.path.join(self.build_lib, versionfile_build)
@@ -651,6 +650,6 @@ class cmd_update_files(Command):
 def get_cmdclass():
     return {'version': cmd_version,
             'update_files': cmd_update_files,
-            'build': cmd_build,
+            'build_py': cmd_build_py,
             'sdist': cmd_sdist,
             }