catch unicode error listing profiles

there can be garbage files on the filesystem, and we shouldn't be bothered by them.
Explicitly state what version of Pandoc is supported in the docs.
underscore missing on notebook_p4

Related with issue https://github.com/ipython/ipython/issues/4312
Merge pull request #4316 from pvilas/master

underscore missing on notebook_p4
Deleted commented addthis toolbar.
Deleted loading of addthis-specific js file and other references.
Use the with statement to open a file.
Merge pull request #4315 from jdfreder/docs_pandoc_version

Explicitly state what version of Pandoc is supported in docs/install
Merge pull request #4318 from minrk/sys.path

fix initial sys.path
Merge pull request #4327 from abhinav-upadhyay/use-with-to-read-file

Use the with statement to open a file.
Merge pull request #4324 from damianavila/remove_addthis

Remove commented addthis toolbar
Merge pull request #4314 from minrk/eaccess

catch EACCES when binding notebook app

can come up for low ports on *ix, or user access control restrictions on Windows.

closes #4308
Merge pull request #4264 from minrk/unicode-list-profiles

catch unicode error listing profiles
Improvements to kernel.js

- dispatch iopub handlers by msg_type
- add Kernel.send_shell_message public API
- use strict (and related fixes)
add Kernel-side widgets
add javascript-side widgets
document widget messages
fix js/Python WidgetManager symmetry

remove some log statements
make js / Python widgets symmetrical

don't enforce creation on Kernel side

also removed weak refs - premature optimization,
we can think about this later.
update widget message spec doc to reflect symmetry