Explicitly set the include_root_in_json flag in Lighthouse::Base

`ActiveResource` 4.0 does not include the root json element by default,
this prevents communication with the lighthouse api which requires this
element. Setting this flag will allow the gem to work with both
`ActiveResource` 3 and 4.
Merge pull request #1 from sqm/update-for-active-resource-4

Explicitly set the include_root_in_json flag in Lighthouse::Base