Don't support Python 2.5 any more (since persistent doesn't).

Clean up dependency and setup test support.

(setup test fails because of circular imports)

setup.py

@@ -30,19 +30,10 @@ from setuptools.extension import Extension
 import os
 import sys
 
-if sys.version_info < (2, 5):
+if sys.version_info < (2, 6):
     print "This version of ZODB requires Python 2.5 or higher"
     sys.exit(0)
 
-
-
-if sys.version_info < (2, 6):
-    transaction_version = 'transaction == 1.1.1'
-    manuel_version = 'manuel < 1.6dev'
-else:
-    transaction_version = 'transaction >= 1.1.0'
-    manuel_version = 'manuel'
-
 # The (non-obvious!) choices for the Trove Development Status line:
 # Development Status :: 5 - Production/Stable
 # Development Status :: 4 - Beta
@@ -151,7 +142,6 @@ def alltests():
                         {}, {}, ['*'])
                     suite.addTest(mod.test_suite())
         elif 'tests.py' in filenames:
-            continue
             mod = __import__(_modname(dirpath, base, 'tests'), {}, {}, ['*'])
             suite.addTest(mod.test_suite())
     return suite
@@ -171,6 +161,8 @@ long_description = str(
     ).decode('latin-1').replace(u'L\xf6wis', '|Lowis|')
     )+ '''\n\n.. |Lowis| unicode:: L \\xf6 wis\n'''
 
+tests_require = ['zope.testing', 'manuel']
+
 setup(name="ZODB",
       version=VERSION,
       setup_requires=['persistent'],
@@ -185,14 +177,14 @@ setup(name="ZODB",
       classifiers = filter(None, classifiers.split("\n")),
       long_description = long_description,
       test_suite="__main__.alltests", # to support "setup.py test"
-      tests_require = ['zope.testing', manuel_version],
-      extras_require = dict(test=['zope.testing', manuel_version]),
+      tests_require = tests_require,
+      extras_require = dict(test=tests_require),
       # XXX: We don't really want to install these headers;  we would
       #      prefer just including them so that folks can build from an sdist.
       headers = ['include/persistent/cPersistence.h',
                  'include/persistent/ring.h'],
       install_requires = [
-        transaction_version,
+        'transaction',
         'persistent',
         'zc.lockfile',
         'ZConfig',