Vagrant development environment configuration.

Starting the update to support ROS Hydro, and a general sprucing up of
the package as a whole.
Increase vagrant VM memory.

Cabal and GHC use quite a lot of memory.
More VM setup.

Install bash-completion for cabal-install.

Add cabal directories to PATH.
Switch away from deprecated attoparsec module.
Simpler use of Typeable for Topics.

With GHC 7.6.3, we can't derive a Typeable instance for Topic, but going
forward hand-written Typeable instances are disallowed. Instead, we now
dynamically type just the payload of a 'Topic IO' as this is the only
thing we need to abstract over to deal with publishing.
Loosened vector constraint on PubSub example.
Initial support for catkin build dependencies.

We need to find package dependencies to generate message
definitions. These are specified somewhat differently in catkin
package.xml files than they were in the previous build system's
manifest.xml files.
We need to link with the right version of Cabal.

We must ensure that roshask's dependency on Cabal is consistent with the
version available when the cabal-install program runs our custom
Setup.hs.

This is fragile and probably not yet right.
Support for working in Cabal sandboxes.

This means that generate message definition packages are installed in
the same sandbox as roshask itself if it is installed in a sandbox.