Update deprecation message for Firestore.#758

Merged

wilhuff merged 3 commits intomasterfrom

rw-logging-deprecation-msg

Feb 8, 2018

Commits on Feb 6, 2018

Update FIRFirestore.h
ryanwilson
authored

Commits on Feb 7, 2018

Fixed style of change.
ryanwilson
committed

Commits on Feb 8, 2018

Provide full command to enable debugging.
ryanwilson
committed