Added 'extras' dependencies

setup.py

@@ -1,5 +1,11 @@
 from setuptools import setup, find_packages
 
+# Requirements to install buffet plugins and engines
+_extra_cheetah = ["Cheetah>=1.0", "TurboCheetah>=0.9.5"]
+_extra_genshi = ["Genshi >= 0.3.5"]
+_extra_kid = ["kid>=0.9.5", "TurboKid>=0.9.9"]
+_extra_mako = ["Mako >= 0.1.1"]
+
 setup(
     name='tw2.forms',
     version='2.0b4',
@@ -24,7 +30,13 @@
     keywords = [
         'toscawidgets.widgets',
     ],
-    tests_require = ['BeautifulSoup', 'nose', 'FormEncode', 'WebTest'],
+    tests_require = ['BeautifulSoup', 'nose', 'FormEncode', 'WebTest'] + _extra_cheetah + _extra_genshi + _extra_kid + _extra_mako,
+    extras_require = {
+        'cheetah': _extra_cheetah,
+        'kid': _extra_kid,
+        'genshi': _extra_genshi,
+        'mako': _extra_mako,
+    },
     classifiers = [
         'Development Status :: 3 - Alpha',
         'Environment :: Web Environment',