Drop Page.section attribute

This attribute goes back to an older design, where
the 'edit page' workflow was different: the edit() method did
part of the work of defining what text you meant to edit. In
the current workflow, text() - which replaced the deprecated
edit() - is only for retrieving text, and save() is supposed
to do all the work of editing the page.

The 'section' attribute is therefore obsolete and dangerous.

mwclient/page.py

@@ -14,7 +14,6 @@ class Page(object):
             return self.__dict__.update(name.__dict__)
         self.site = site
         self.name = name
-        self.section = None
 
         if not info:
             if extra_properties:
@@ -147,11 +146,9 @@ class Page(object):
         try:
             rev = revs.next()
             text = rev['*']
-            self.section = section
             self.last_rev_time = rev['timestamp']
         except StopIteration:
             text = u''
-            self.section = None
             self.last_rev_time = None
         if not expandtemplates:
             self.edit_time = time.gmtime()
@@ -172,14 +169,6 @@ class Page(object):
         if not self.can('edit'):
             raise mwclient.errors.ProtectedPageError(self)
 
-        if self.section is not None and section is None:
-            warnings.warn('From mwclient version 0.8.0, the `save()` method will no longer ' +
-                          'implicitly use the `section` parameter from the last `text()` or ' +
-                          '`edit()` call. Please pass the `section` parameter explicitly to ' +
-                          'the save() method to save only a single section.',
-                          category=DeprecationWarning, stacklevel=2)
-            section = self.section
-
         if not self.site.writeapi:
             raise mwclient.errors.NoWriteApi(self)