Rename generate man page command

build_manpage is more obvious than create_manpage as most python
setuptools around generation of output ready for install are prefixed
with 'build_'.

build_manpage.py

@@ -22,10 +22,10 @@ import argparse
 from distutils.core import Command
 
 
-class CreateManpage(Command):
+class BuildManpage(Command):
 
     user_options = []
-    command_name = 'create_manpage'
+    command_name = 'build_manpage'
 
     def initialize_options(self):
         from git_upstream import main

setup.cfg

@@ -22,7 +22,7 @@ classifiers =
     Operating System :: OS Independent
 
 [global]
-commands = create_manpage.CreateManpage
+commands = build_manpage.BuildManpage
 
 [files]
 packages =

tox.ini

@@ -19,7 +19,7 @@ commands =
   python setup.py testr --coverage
 
 [testenv:doc]
-commands = python setup.py create_manpage
+commands = python setup.py build_manpage
 
 [testenv:venv]
 commands = {posargs}