Clean up simple_test.py:

  - Use test class for better setup/teardown methods and sharing data.

  - Use temporary directory to do the conversion in to avoid cluttering
    the test/ directory.
Systematically test main() with all formats, not just 'rst' and 'html'.
Add an 'unexecuted' cell (with missing prompt_number) to test.ipynb.

This makes some tests fail because they assume that each cell has a
'prompt_number' attribute.
Quick fix for failing tests. This will be cleaned up soon.

This is only a quick fix to make the tests pass. Note that some tests
which access the 'prompt_number' attribute were not affected by the
additional unexecuted cell in tests/test.ipynb which was added in
commit ec19b407dee30fb7e692ce753af9fc5bd3808f8f. So this probably
indicates that not all corner cases are covered.
Replace ad-hoc/broken code with safe method to extract the prompt_number of a cell.

The helper function returns the converter's blank symbol ('&nbsp;' for HTML,
space for other converters) if the cell doesn't have a prompt_number.
PEP8-ify several files
Unused imports.
PEP8-ify rest of the repository.
Fixed weird ImportError introduced during rebase.
Merge pull request #58 from maxalbert/test_cleanup_and_bugfix

Test cleanup and bugfix
Merge PR 52 from @dwf and @rcl33

PDF conversion - control type of content output

I like to produce PDFs from notebooks as a nice way to get printable
output. I'm often more interested in the discussion (in Markdown cells)
and the results (matplotlib figures) than the Python code used to create
them. So I've added an option to exclude the Python source ("-e source"
option) or the output ("-e output", although I haven't found this one
useful).

They can be combined e.g. "-e source,output". I've also included small
fixes to help LaTeX work with unusual characters in filenames, and a
command line option to specify the user preamble (for which there was
already code)

Conflicts:
	converters/base.py
Merge pull request 56 from dwf/nbconvert

Make repository PEP8-compliant

So that we don't introduce poorly formatted code into the main
repository when we merge.

Conflicts:
	converters/html.py
	converters/latex.py
	converters/python.py
	nbconvert.py
	tests/test_simple.py
Added an option to disable syntax highlighting in code blocks. Simply add the -p or --plain_output tag to the command. This is a fix for issue #21
Changed name of argument command to remove highlighting; also added a fallback of True to the highlight argument in several places in case it's called without said argument.
Changed the name of the highlight boolean to highlight_code in order to differenciate it from the highlight function.
Rearranged order of arguments for functions dealing with highlight_code in order to preserve backwards compatability.
Defined highlight_code at class level to comply with IPython coding style.
Fixed bad variable names in nbconvert.py and html.py.
Match existing highlight_source convention.

ConverterMarkdown already had something called highlight_source,
so this switches around other classes to match. Arguably this is
not as descriptive as it should be, since code within Markdown
cells is still highlighted.
Embed LaTeX output from pyout into equation* environment