Removes completion block from pagination calls.

[diegosanchezr]

Now DataSource is responsible for notifying the exact type of change. This implicitly allows more flexibility in the dataSource ( like ignoring such a request! ) and reduces entry points from where changes are enqueued

[codecov-io]

Current coverage is 62.17%

Merging #45 into dev will increase coverage by +0.16% as of a6f28ee

@@              dev     #45   diff @@
=====================================
  Files          57      57       
  Stmts        2901    2818    -83
  Branches        0       0       
  Methods         0       0       
=====================================
- Hit          1799    1752    -47
  Partial         0       0       
+ Missed       1102    1066    -36

Review entire Coverage Diff as of a6f28ee

Powered by Codecov. Updated on successful CI builds.