Update With statement

[Felipe]

In Python 3.4.2 (and possibly earlier), the With statement has been updated to use withitem nodes. (link to 3.4 grammar)The docs should be updated to reflect this change as follows:

• With: A with block. items is a list of withitem nodes containing the context managers and body is a list of nodes inside the statement
• withitem: A single context manager in a with block. context_expr is the context manager, often a Call node. optional_vars is a Name, Tuple or List for the as foo part, or None if that isn’t used.

[Thomas Kluyver]

Update With node for 3.3+

Fixes issue #3

→ <<cset 5e5f4fc729d9>>

[Thomas Kluyver]

Thanks for letting me know, should be fixed now.