Upgrade to RSpec 3

As part of this upgrade, the following changes were made to fix some
deprecation warnings and unsupported syntax:

  * Replacement of `its` with an `it` block equivalent
  * Renaming of `failure_message_for_should` -> `failure_message` and
    similar for negated form
  * Replacing `be_true` with `== true` and `be_false` with `== false`

We've elected to keep the `should` syntax because it is convenient to do
so; we may switch entirely to `expect` at some point in the future.

Change-Id: I936bb63e33a301264c48185e7d91ba7ad04a87bf
Reviewed-on: http://gerrit.causes.com/38489
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>
Quiet down cherry-pick integration spec

This spec was printing out messages like:

    error: could not apply 79d0feb... Add Branch 2 addition
    hint: after resolving the conflicts, mark the corrected paths
    hint: with 'git add <paths>' or 'git rm <paths>'
    hint: and commit the result with 'git commit'

To prevent the spec suite from having noisy output, redirect STDERR for
the cherry-picking code to /dev/null.

Change-Id: Iba67b179cf4e0f87f805cb28a362ba276658b24c
Reviewed-on: http://gerrit.causes.com/38490
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>