Update omnibus to pull in updated `ffi-yajl` and `libyajl2`

Before this update `bundle install` fails as follows:

```
vagrant@chef-ubuntu-1204:~/omnibus-chef$ bundle install
Fetching gem metadata from https://rubygems.org/.........
Fetching additional metadata from https://rubygems.org/..
Fetching git://github.com/opscode/omnibus-ruby.git
Fetching git://github.com/opscode/omnibus-software.git
Installing addressable 2.3.6
Installing cabin 0.6.1
Installing arr-pm 0.0.9
Installing backports 3.6.0
Installing chef-sugar 1.3.0
Installing ffi 1.9.3
Installing childprocess 0.5.3
Installing clamp 0.6.3

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    /opt/rubies/ruby-2.1.1/bin/ruby extconf.rb
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:
	--with-opt-dir
	--without-opt-dir
	--with-opt-include
	--without-opt-include=${opt-dir}/include
	--with-opt-lib
	--without-opt-lib=${opt-dir}/lib
	--with-make-prog
	--without-make-prog
	--srcdir=.
	--curdir
	--ruby=/opt/rubies/ruby-2.1.1/bin/ruby
/opt/rubies/ruby-2.1.1/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- libyajl2 (LoadError)
	from /opt/rubies/ruby-2.1.1/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
	from extconf.rb:3:in `<main>'

extconf failed, exit code 1

Gem files will remain installed in /home/vagrant/.gem/ruby/2.1.1/gems/ffi-yajl-0.2.0 for inspection.
Results logged to /home/vagrant/.gem/ruby/2.1.1/extensions/x86_64-linux/2.1.0-static/ffi-yajl-0.2.0/gem_make.out
An error occurred while installing ffi-yajl (0.2.0), and Bundler cannot continue.
Make sure that `gem install ffi-yajl -v '0.2.0'` succeeds before bundling.
```

I'm not sure what has been fixed in the updated versions of `ffi-yajl` and `libyajl2` as @lamont-granquist has not pushed his released code to GitHub. As these gems are dependancies for our software we need to use a grown-up release process for them just like we would for Chef, Ohai and Omnibus. We should also move both gems to the `opscode` GitHub organization.

/cc @opscode/release-engineers @opscode/client-engineers @jmink