nixos/logstash: add enableWeb option to enable kibana web interface
add nix-prefetch-zip
fix bzr prefetcher on darwin
Fix sudo not installing due to timedir deprecation
keep fallback visudo editor as nano
numexpr: new package, version 2.4

Description from the numexpr project page [1]:
> Numexpr is a fast numerical expression evaluator for NumPy. With it,
> expressions that operate on arrays (like "3*a+4*b") are accelerated and use
> less memory than doing the same calculation in Python.

I am adding it, because it is a dependency of the pytables package.

[1]: https://github.com/pydata/numexpr
hdf5: Add zlib as optional dependency

This adds addition compression modes to the hdf5 library.

I am adding this, because pytables depends on it.
szip: Fix source hash

The hash code of the downloaded source tar-ball was not identical to the one
specified in the nix-expression. This commit fixes that problem.
hdf5: Add szip as an optional dependency

This adds additional compression modes to hdf5.

Note: The szip license may not be compatible with everyone's use case. Hence,
it is an optional dependency.
hdf5: Update to 1.8.13
tables: add new package, version 3.1.1

From the project page [1]:
> PyTables is a package for managing hierarchical datasets and designed to
> efficiently and easily cope with extremely large amounts of data.

It offers read/write access to hdf5 archives through a hierarchical interface.

I am adding it, because pandas depends on tables for hdf5 read/write
functionality.

Note: The name is a bit of an issue. The project is called pytables, whereas
the python module is simply called tables. I chose to name the nix-expression
tables for consistency with the source-tarball and the module name.

[1]: http://www.pytables.org/moin
pandas: Update to 0.14.0
require gnused for all prefetch scripts
Add gox and packer packages
update serfdom to v0.6.2
add etcd package
add etcdctl package
add fleet package
add nsq package
add gocode package