Grape v1.4.0 fixes a memory leak that was present in v1.3.3
(https://github.com/ruby-grape/grape/pull/2084).

Full list of changes:

* https://github.com/ruby-grape/grape/blob/master/CHANGELOG.md
* https://github.com/ruby-grape/grape/compare/v1.3.3..v1.4.0