pagination in getAllActivitiesByActor
Pagination service and unit tests
Applied Pagination to all controllers
Added pagination as a Function instead of singleton, renamed offset for page, unit tests
Added pagination as a Function instead of singleton, renamed offset for page, unit tests
Added offset parameter to the pagination service
Replaced all uses of pagination to use the function instead of singleton object
Merge pull request #48 from natgeo/feature/MIE-1564

[MIE-1608] Added a simple pagination service and implemented it in every endpoint returning lists.
Merge branch 'develop' of github.com:natgeo/activitystreams