update sources to point to github

sources.cfg

+[buildout]
+svn-zope-org = ^
+github = git://github.com/zopefoundation
+
 [sources]
-AccessControl = svn ^/AccessControl/branches/2.13
-Acquisition = svn ^/Acquisition/trunk
-DateTime = svn ^/DateTime/branches/2.12
-DocumentTemplate = svn ^/DocumentTemplate/trunk
-ExtensionClass = svn ^/ExtensionClass/trunk
-initgroups = svn ^/initgroups/trunk
-Missing = svn ^/Missing/trunk
-MultiMapping = svn ^/MultiMapping/trunk
-nt_svcutils = svn ^/nt_svcutils/trunk
-Persistence = svn ^/Persistence/trunk
-Products.BTreeFolder2 = svn ^/Products.BTreeFolder2/trunk
-Products.ExternalMethod = svn ^/Products.ExternalMethod/trunk
-Products.MIMETools = svn ^/Products.MIMETools/trunk
-Products.OFSP = svn ^/Products.OFSP/trunk
-Products.PythonScripts = svn ^/Products.PythonScripts/trunk
-Products.StandardCacheManagers = svn ^/Products.StandardCacheManagers/trunk
+AccessControl = git ${buildout:github}/AccessControl branch=2.13
+Acquisition = git ${buildout:github}/Acquisition
+DateTime = git ${buildout:github}/DateTime branch=2.12
+DocumentTemplate = git ${buildout:github}/DocumentTemplate
+ExtensionClass = git ${buildout:github}/ExtensionClass
+initgroups = git ${buildout:github}/initgroups
+Missing = git ${buildout:github}/Missing
+MultiMapping = git ${buildout:github}/MultiMapping
+nt_svcutils = git ${buildout:github}/nt_svcutils
+Persistence = git ${buildout:github}/Persistence
+Products.BTreeFolder2 = git ${buildout:github}/Products.BTreeFolder2
+Products.ExternalMethod = git ${buildout:github}/Products.ExternalMethod
+Products.MIMETools = git ${buildout:github}/Products.MIMETools
+Products.OFSP = git ${buildout:github}/Products.OFSP
+Products.PythonScripts = git ${buildout:github}/Products.PythonScripts
+Products.StandardCacheManagers = git ${buildout:github}/Products.StandardCacheManagers
 Products.ZCatalog = svn ^/Products.ZCatalog/branches/2.13
 Products.ZCTextIndex = svn ^/Products.ZCTextIndex/trunk
 Record = svn ^/Record/trunk
 tempstorage = svn ^/tempstorage/trunk
 zExceptions = svn ^/zExceptions/trunk
-ZODB3 = svn ^/ZODB/trunk
 ZopeUndo = svn ^/ZopeUndo/trunk
-ZConfig = svn ^/ZConfig/trunk