Added stats/contributors client & response objects

Not a fan of those suppress messages on weekly hash. Will see if we can
clean this up :soon:
Stubbed implementation of IStatisticsClient
Updated signature to include repo name and owner

Also return a list of contributors because.reasons (being that is what
the api returns)
renamed parameter
Implement client
Test stats client get contributors
:lipstick: renamed to GetContributors
Added Statistics Client
:lipstick:
ObservableStats Client
Observable Client tests
Added intergration tests for contributors api
Retry until call is successful

This is crude I know, but will be revisited once all apis implemented
 a work around for simple json support for empty root nodes
Get commit activity for the last year
Simple intergration test for commit activity
One test fixture to rule them all

Because having them as nested classes is pointless
Extra asserts for contributors intergration tests
:lipstick:
Extra asserts for this years commit stats