Split navigation to separate "scipy stack" and "scipy library" parts.

This makes the Scipy library pages a sub-site of the main site.
Bias the top-level site less towards Numpy+Scipy
scipylib: replace the 'distributions' section with a link to scipy stack install instructions
scipylib: fix build instructions navigation
Replace Scipy -> Scipy library in a number of places
MAINT: Announce NumPy 1.8.0 release.
Merge pull request #34 from charris/announce-1.8.0

MAINT: Announce NumPy 1.8.0 release.
MAINT: remove conference/

The conference site is now in a separate repo.
Update topical-software.rst

Adding some modules that I have written or worked on.
pyLuminous, aestimo, plotexploter_gui
MAINT: Announce NumPy 1.7.2rc1 release
Update Arch urls to properly find Arch's num/scipy packages
Merge pull request #38 from Ivoz/patch-1

Update Arch urls to properly find Arch's num/scipy packages
Merge pull request #37 from juliantaylor/numpy-1.7.2rc1

MAINT: Announce NumPy 1.7.2rc1 release
Merge pull request #36 from robochat/patch-1

Update topical-software.rst
Merge pull request #35 from pv/rmconf

MAINT: remove conference/
Added Plotly to "Working Environments" and "tools with a (mostly) 2-D focus"
added NIFTY under Bayesian Statistics
Merge pull request #40 from mselig/patch-1

added NIFTY under Bayesian Statistics
Merge pull request #39 from mattsundquist/patch-1

Added Plotly to "Working Environments" and "tools with a (mostly) 2-D focus"
Merge pull request #31 from pv/splitnav

Split scipylib to a more clear sub-site