Backport PR #5713: Fix a NameError in IPython.parallel

This was causing test failures on ShiningPanda.
Backport PR #5714: log error message when API requests fail

we have been silencing our helpful log messages when they are on JSON API requests
Backport PR #5715: log all failed ajax API requests

and add a warning dialog when New Notebook fails.

closes #3085

We should probably have more dialogs for failed requests, but logging everything is at least a start.
Backport PR #5716: Add booktabs package to latex base.tplx

Trivial fix to include the booktabs package in the base.tplx which is required for tables created with pandoc > 1.12.2 (see [releases](http://johnmacfarlane.net/pandoc/releases.html#pandoc-1.12.2-2013-12-07)) - fixes #5690
Backport PR #5732: Quick typo fix in nbformat/convert.py
Backport PR #5744: Describe using PyPI/pip to distribute & install extensions

From discussion on gh-5742