document flow-parser tokens property
document flow-parser tokens property

Summary: Fixes https://github.com/facebook/flow/issues/8594

Reviewed By: gkz

Differential Revision: D28452864

fbshipit-source-id: 6f275e676e15c117c071f6e84d38543f4ac7af65

mroch/flow,facebook/flow,facebook/flow,facebook/flow,facebook/flow,mroch/flow,mroch/flow,mroch/flow,mroch/flow,mroch/flow,facebook/flow,facebook/flow,facebook/flow,mroch/flow