Fix typo

Document why newTransaction is only called by begin.

We have no C extensions, and therefore do not need to exclude their
derived files in 'MANIFEST.in'.

extended-info -> extension

I'll make the transaction release and then I'll push an update to the ZODB PR that works with the change.

renamed to ``extension``.

Hate bytes

See: https://groups.google.com/forum/#!topic/zodb/U0H1kTh_dY4

URGENT: _extension needs to be settable

  attribute to be settable and it wasn't.

Run docs doctests in travis

I need this for some work I'm about to do so...

Yay, doctests work in travis

Also cache eggs

Because sphinx doesn't work with it.

Also, I wonder if scripts can be multiple lines.