Add rake synthesize task to speed up builds

Without this patch it's difficult to synthesize a bunch of individual
builds because the behavior is at the end of the large rake crossfader
task.  This patch addresses the problem by moving the build and
synthesize behaviors into their own builder class instance method.  A
new task calls the instance method on demand.
Fix name of crossfader ruby runtime package

The package name didn't follow the same pattern as the other packages.
In addition, the main package bundle didn't have the Mac OS X minor
version included in the file name which is a problem for people on new
minor versions of the OS.
Fix side effect on package_id method

Without this patch calling the package_id method has the side effect of
changing the name.  This is a problem because the wrong name is used to
produce the package after the package_id method is called.

The fix is to eliminate the side effect by creating a new string
instance.
Clean up mac version in xml filename

The distribution XML filename doesn't match the package filename without
this patch.
Add Command Line Tools October 2013
Add Command Line Tools to final package

Without this patch the final package does not include the dependency on
the command line tools package.  This patch addresses the problem by
linking in the Command Line Tools package downloaded from
developer.apple.com for October 2013 for Mac OS X 10.8
Do not link Command Line Tools
Re-enable linking of Command Line Tools

It turned out the error I was facing was because `xcode-select` was
referring to an old version of xcode during the build.  Selecting the
most recent version with `xcode-select -switch /Applications/Xcode.app`
fixed the problem.
Write final package artifact to artifacts/

Without this patch the build archives are growing quite large.  We're
copying a lot of data we don't really need to archive after each build.
The only thing that really matters is the distribution archive itself so
this patch changes the crossfader task to write the distribution package
to the artifacts/*.pkg directory.
Merge branch 'crossfader'

* crossfader:
  Write final package artifact to artifacts/
  Re-enable linking of Command Line Tools
  Do not link Command Line Tools
  Add Command Line Tools to final package
  Add Command Line Tools October 2013
  Clean up mac version in xml filename
  Fix side effect on package_id method
  Fix name of crossfader ruby runtime package
  Add rake synthesize task to speed up builds