Install gem list into global gemset

Without this patch each ruby version does not include a default set of
gems.  This is a problem because each ruby version crossfader manages
should ideally include at least bundler.  This patch addresses the
problem by loading a special YAML file located at
config/crossfader_ruby_210_gems.yaml

If the YAML file does not exist then a default global gemset of bundler
is automatically installed for each Ruby version.
Make ruby gemset directories admin writable

Without this patch end users of crossfader cannot install gems without
dropping to root access levels.  This is a problem because sudo resets
the environment which makes usability more difficult.

This patch fixes the problem by packaging crossfader in a manner that
uses recommended permissions for nearly everything except the gemset
directory which is root:admin with 775 unix permissions.
Add version identifier to /opt/crossfader/version.txt

Without this patch there is no version identifier for the installed
version of the full crossfader package.  This is a problem because the
crossfader executable command returns the gem version of crossfader, not
the actual build version.  We need to store and write the build version
in the package in order to display it to the user.

This patch addresses the problem by writing
/opt/crossfader/version.txt when building and before packaging
the crossfader runtime environment itself.  This file is managed by a
small, special package with the same version as the single file written.
Display build version from `crossfader --version`

Without this patch the end user doesn't have an way to easily check
which version of crossfader is currently installed.  When we say
"crossfader version" we generally mean the build version, which is all
of the components in the main distribution package.  This patch augments
the crossfader gem version with an additional build version read from
/opt/crossfader/version.txt
Set CROSSFADER_RUBY during shellinit

Without this patch the CROSSFADER_RUBY environment variable is not set
when initializing the shell environment for crossfader.  This makes it
difficult to hand off the currently initialized environment to a sudo
initialized environment with something like `sudo crossfader
--ruby=$CROSSFADER_RUBY --gemset=$CROSSFADER_GEMSET`.

This patch addresses the problem by setting CROSSFADER_RUBY just like
CROSSFADER_GEMSET is defined during shell initialization.

In addition this patch uses XFADE_PATH_ORIG if it's present in the
enviornment.  This has the behavior of using the original PATH when
constructing a new PATH from a nested invocation of crossfader.
Fix crosfader --version output

Without this patch there is a trailing newline while reading the
crossfader build version file.  This patch addresses the problem by
reading only the first line of the file and making sure trailing
whitespace is chomped off.