Updated setup.py with new dependencies.

Actually, the slapos.libnetworkcache has new dependeincies because
M2Cryto is required to handle the signatures inside NetworkcacheClient class
and the argparse is required by signature.py script.

setup.py

@@ -15,6 +15,14 @@ long_description = (
         read('CHANGES.txt')
     )
 
+additional_install_requires = []
+# Even if argparse is available in python2.7, some python2.7 installations
+# do not have it, so checking python version is dangerous
+try:
+  import argparse
+except ImportError:
+  additional_install_requires.append('argparse')
+
 setup(
     name=name,
     version=version,
@@ -25,12 +33,17 @@ setup(
     install_requires=[
       'setuptools', # for namespace
       'M2Crypto',
-    ],
+    ] + additional_install_requires,
     classifiers=[
       'Development Status :: 4 - Beta',
       'License :: OSI Approved :: GNU General Public License (GPL)',
       'Programming Language :: Python :: 2',
       ],
+    entry_points={
+      'console_scripts': [
+        'generate-signature-key = slapos.signature:run',
+      ]
+    },
     zip_safe=True,
     packages=find_packages(),
     namespace_packages=['slapos'],