One of SchemaProvider switches needs more testing

[neomerx]

While working on #64 I noticed $isShowRelShipsInIncluded has no effect on any tests and connected only to parsing strategy.

Possible actions

• remove as unused
• add tests that covers this behaviour

[neomerx]

Should be removed as unused for the reasons

• I don't see any reasons why relationships might be excluded from result (but attributes left)
• This switch is not actually used while adding relationships in included objects

[neomerx]

Doc updated https://github.com/neomerx/json-api/wiki/Schemas#additional-encode-tuning-options