Update ruby-rspec-core to 3.4.2.

### 3.4.2 / 2016-01-26
[Full Changelog](http://github.com/rspec/rspec-core/compare/v3.4.1...v3.4.2)

Bug Fixes:

* Fix `rspec --profile` when an example calls `abort` or `exit`.
  (Bradley Schaefer, #2144)
* Fix `--drb` so that when no DRb server is running, it prevents
  the DRb connection error from being listed as the cause of all
  expectation failures. (Myron Marston, #2156)
* Fix syntax highlighter so that it works when the `coderay` gem is
  installed as a rubygem but not already available on your load path
  (as happens when you use bundler). (Myron Marston, #2159)

(taca)