[docs] [issue19900] improve pickle intro

[Roundup Robot]

Roundup Robot added the comment:

New changeset 609325d187bf by Antoine Pitrou in branch '3.3':
Issue #19900: improve generalities at the start of the pickle module doc
http://hg.python.org/cpython/rev/609325d187bf

New changeset 595b8f82569c by Antoine Pitrou in branch 'default':
Issue #19900: improve generalities at the start of the pickle module doc
http://hg.python.org/cpython/rev/595b8f82569c

----------
nosy: +python-dev

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue19900>
_______________________________________