DOC: Update the MATLAB section of the 'io' tutorial:
* Mention the 'whosmat' function.
* Fix an indentation problem.
* Update output in the examples.
* Rephrase and expand a few sentences.
DOC: capitalize Bode, fix "transfer function" mistake
ENH reproducible scipy.sparse.rand
DOC: vanity
ENH prevent copy in dok_matrix.tocoo
Merge pull request #445 from larsmans/dok-tocoo

ENH: sparse: prevent copy in dok_matrix.tocoo
Merge pull request #443 from larsmans/sparse-rand

ENH: sparse: add random_state option to scipy.sparse.rand
Merge pull request #440 from WarrenWeckesser/doc-io-tutorial

DOC: Update the MATLAB section of the 'io' tutorial
Update the parameter documentation in curve_fit

The documentation describing the `sigma` parameter of the
`optimize.curve_fit` function was updated to remove the reference
to representing the standard deviation of the data.  This is 
misleading because the `sigma` value is used purely as a relative
weighting factor.

See also:
http://mail.scipy.org/pipermail/scipy-user/2013-February/034191.html
Merge pull request #446 from taldcroft/curve-fit-sigma-doc

Update the parameter documentation in curve_fit
Merge pull request #439 from endolith/ltisys_docstrings

DOC: capitalize Bode, fix "transfer function" mistake