devel/ruby-rspec-core: update to 3.7.1

### 3.7.1 / 2018-01-02
[Full Changelog](http://github.com/rspec/rspec-core/compare/v3.7.0...v3.7.1)

Bug Fixes:

* Work around duplicate config hook regression introduced
  by Ruby 2.5's lazy proc allocation. (Myron Marston, #2497)

### 3.7.0 / 2017-10-17
[Full Changelog](http://github.com/rspec/rspec-core/compare/v3.6.0...v3.7.0)

Enhancements:

* Add `-n` alias for `--next-failure`. (Ian Ker-Seymer, #2434)
* Improve compatibility with `--enable-frozen-string-literal` option
  on Ruby 2.3+. (Pat Allan, #2425, #2427, #2437)
* Do not run `:context` hooks for example groups that have been skipped.
  (Devon Estes, #2442)
* Add `errors_outside_of_examples_count` to the JSON formatter.
  (Takeshi Arabiki, #2448)

Bug Fixes:

* Improve compatibility with frozen string literal flag. (#2425, Pat Allan)

(taca)