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
Introduce standard structure from coding guidelines in converters/.
Give highlight_source a proper boolean default.
Declare several members at the class level.
Improve conversion to latex of output cells

Improve the latex convert possibilites of pyout and display_data cells.

Detailed changes:

 - set display_data_priority for latex output to start with 'latex'
 - use numbered equations
 - define relative figure size instead of absolute
 - specify image file position relative to input file position
 - pyout.text is only rendered if latex representation is not available
 - place display_data_format_latex output in equation environment
 - some minor code clean-up
Use equation_env variable, PEP8 adaptation
Simplify control flow with nesting.

These two branches were mutually exclusive and naturally structured
as if { if ... else ... }, rather than two conjunctive clauses.
More descriptive comment headers.
Fix test, add highlight_source to ConverterPy.

This is a bit odd and inelegant but short of a
"supports_highlight_source" class-level attribute and logic to handle it
in the main() entrypoint, I'm not sure how else to resolve it.
Clean up definition/constructor of Converter.
More documentation.
Merge pull request #61 from dwf/syntax_highlight

Syntax highlighting redux + other cleanup
fix typo after #61 merge making ./nbconvert crash

hilight_code -> highlight_source