Remove pvm script no longer needed
Add xfade-run script to setup environment

Without this patch there isn't an easy way to install Gem dependencies
into the crossfader runtime environment itself.  This is a problem
because we need a way to easily run commands inside of an environment
that has all of the libraries we need.

We can't simply install to the system gem location since we need to keep
that gem path clean for other uses.

This patch addresses the problem by initializing the gem home at
/opt/crossfader/runtime/gemsets/crossfader.  In addition the global
gemset is initialized.

This should help packaging tasks that can produce an updated tools
package by simply packaging up the
/opt/crossfader/runtime/gemsets/crossfader directory.
Package crossfader runtime gemset

This gemset will contain all of the libraries required to run the
crossfader gem command itself.  This is expected to be minimal, but in
the event it grows it will be nice to have this out of the way and not
polluting the interpreter's gem library path.
Add crossfader gem scaffold from bundler

This gem scaffold was produced using bundler:

    bundle gem --bin crossfader
Update crossfader gemspec summary and description

This patch simply fills out a basic summary and description.
Install crossfader script and package in the gems

Without this patch we don't actually have the crossfader command line
utility to manage GEM_HOME and GEM_PATH.  This patch addresses the
problem by installing the script from the crossfader gem directory.