Added exclusion code for rst, markdown, and html.
improve extraction of code cells, support for ipy prompt

When experimentally converting a part of the scipy-lecture-notes:

http://scipy-lectures.github.com/intro/language/basic_types.html

Which is written with sphinx and the rst looks like:

https://raw.github.com/scipy-lectures/scipy-lecture-notes/master/intro/language/basic_types.rst

I encountered two issues. Firstly, if there is output in between prompt lines,
for example:

    >>> 7 * 3.
    21.0
    >>> 2**10
    1024
    >>> 8 % 3
    2

This would become a single cell in the ipython notebook, which when executed
gives only '2' as output. But my guess here is what one wants is for each
prompt to be in its own cell. Thus, when teaching you could show the output of
each statement interactively, very similar to the way they are displayed in
sphinx.

I refactored the conversion in the 'visit_literal_block' function to be a state
machine, which looks for consecutive prompts, and bundles these into a single
cell. So, for example:

    >>> a = 3
    >>> b = 2
    >>> a / b
    1
    >>> a / float(b)
    1.5

Results in two cells.

The second improvement is to look for ipython prompts too. Since we are using
the ipython_console_highlighting.py sphinx extension, some code examples use
the ipython prompt. Searching for these is done via regex. Maybe someone has a
better regex than mine?
fix the regex, need at least one digit
remove fake files
add __init__.py for nbviewer (this shouldn't be necessary)
use notebookapp.DEFAULT_STATIC_FILES_PATH to get static path

allows use of nbconvert with system packaged versions of IPython
closes #97
add heading-anchor

following ipython/ipython#3064
Merge pull request #112 from juliantaylor/static-path

use notebookapp.DEFAULT_STATIC_FILES_PATH to get static path

allows use of nbconvert with system packaged versions of IPython
closes #97
fix output div ordering in html

fixes ipython/nbviewer#17
fix div hierarchy for outputs

for reals this time

adds `output` block, and puts the prompt output inside the new `output` block,
to match the html flow.
Grammar fixes in README (mostly plurality)
Grammar fixes, run on sentence trim.
Better wording for pandoc in package managers
Merge pull request #111 from jdfreder/master

Sphinx output style improvements
Merge pull request #105 from Carreau/rmfakefix

remove fake files
fix writing both kind of figures

split figures into 2 kinds text and binary

fixes #107
Merge pull request #108 from Carreau/binfig

fix writing both kind of figures
Merge pull request #116 from rgbkrk/master

Grammar fixes
proof of concept of pdf generation by chaining a pdflatex call onto the end of the latex converter
don't use custom nbcv for plain-Python config files