update gems

[monfresh]

• Remove binding_of_caller gem
• Update reek from 6.1.0 to 6.1.1
• Update rspec-rails from 5.1.1 to 5.1.2
• Update rubocop from 1.26.1 to 1.28.2
• Update more gems with bummr

[codeclimate[bot]]

Code Climate has analyzed commit b6474047 and detected 2 issues on this pull request.

Here's the issue category breakdown:

Category	Count
Duplication	2

The test coverage on the diff in this pull request is 50.0% (80% is the threshold).

This pull request will bring the total coverage in the repository to 98.4% (0.0% change).

View more on Code Climate.