Move build_manpage utility to doc area

Change-Id: I1f440d5be6eb7e14c8f8a5dfbcdcfcaa71ce1ef7

setup.py

@@ -14,9 +14,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import os
 import setuptools
+import sys
 
 
+# build_manpage command added under doc/utils
+sys.path.insert(0, os.path.abspath('./doc/utils'))
+
 setuptools.setup(
     setup_requires=['pbr'],
     pbr=True)