Fixed #grape_documentation issue, added integration tests

- #grape_documentation no longer uses the type: key, because grape raised an
  exception when scalar values were parameterized as arrays (id[]=1&id[]=2)
- Added integration tests
  - Fixed a couple of issues regarding integration with grape
Merge pull request #6 from Adaptly/pc-fix-implicit-arrays

Fixed #grape_documentation issue, added integration tests