RF: disable rdirective extension

rdirective was giving an error on load, of form:

    File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/io.py", line 1515, in write
        s.__class__.__name__)
    TypeError: can't write str to text stream

It seems that io.py here is expecting unicode from the
InteractiveRunner, but got a str type.  IPython 0.13.1, R 2.12.1
RF: add math_dollar sphinx extension

The math_dollar extension is nice for adding little fragments of latex
as $p = 1$ rather than :math:`p = 1`.
BF: re-enable Makefile html build for testing

html build target was looking in the Makefile directory rather than the
source subdirectory.
RF: fix up latex markup and other docstrings

Various problems with LaTeX markup not working in docstrings:

* ``r"""`` sometimes needed in docstring to protect backslashes in math
  markup
* docstring templating causing errors for docstrings which had not yet
  been filled in from the class ``_doc_dict`` definitions dictionary
* Some small LaTeX errors (I think)
* Some stray edits for Numpy docstring standard comformance and
  whitespace

Testing with:

    cd doc
    ln -s ../api source/api
    make html
NF: idea for docstring template decorators

Try setting and using docstring templates through decorators.
NF : add decorator using objective templates

There's a pattern like this in the atom classes::

    objective_template = r"""\|%(var)s\|_1"""
    _doc_dict = copy(atom._doc_dict)
    _doc_dict['objective'] = objective_template % {'var': r'x + \alpha'}

Make a decorator to set ``objective`` automatically from class
attributes ``objective_template`` and ``objective_vars``.
RF: use the doc_templater decorators for docstrings

User ``@objective_doc_templater`` and method decorators to inherit and
modify docstrings.
Merge pull request #13 from matthew-brett/fix-docstrings

Fix docstrings