Update bundle

I was having trouble getting Nokogiri (1.5.6) to build locally under
rbenv-managed Ruby 1.9.3-p392, which in turn meant that I couldn't run
the spec suite.

This commit is the result of running a `bundle update`, which bumps
Nokogiri to 1.6.0 (which builds fine).

Other bumps included in this commit:

  diff-lcs                      1.1.3  -> 1.2.4
  rspec                         2.12.0 -> 2.13.0
  rspec-core                    2.12.0 -> 2.13.0
  rspec-expectations            2.12.0 -> 2.13.0
  rspec-mocks                   2.12.0 -> 2.13.0
  mini_portile                  [n/a]  -> 0.5.0

Change-Id: I3e533fef56e695502af3ce52afaad5c6e6577229
Reviewed-on: https://gerrit.causes.com/23503
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Joe Lencioni <joe.lencioni@causes.com>